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THE  NORTH  AMERICAN  SPECIES 

.  .  OF  .  . 

DIAPTOMUS 

.  .  BY  .  . 

FREDERICK  WILLIAM  SCHACHT. 


TH  ESI8 

FOR  THE  DEGREE 

...OF... 

BACHELOR  OF  SCIENCE 

.  .  IN  THE  .  . 

NATURAL  SCIENCE  GROUP, 
COLLEGE  OF  SCIENCE, 

UNIVERSITY  OF  ILLINOIS. 


1897. 


I 


f 


Article  III. — The  North  American  Species  of  Diaptomus. 
By  Frederick  William  Schacht. 


INTRODUCTION. 

The  first  published  reference  to  that  group  of  genera  of 
Entomostraca  now  known  under  the  family  name  of  Centro- 
pagidce  is  contained  in  0.  F.  Muller's  "Entomostraca  seu 
Insecta  testacea  quae  in  aquis  Daniae  et  Norvegiae  repent, ;' 
etc.,  published  at  Frankfort-on-the-Main  in  1785,  in  which 
paper  certain  copepod  species  now  included  under  the  genus 
Diaptomus  were  treated  under  the  general  name  of  Cyclops. 
Species  of  Diaptomus  were  later  described  by  Jurine  ('20) 
under  Monoculus,  but  the  genus  Diaptomus  was  first  estab- 
lished by  Westwood  ('36).  Various  names  have  since  been 
applied  more  or  less  closely  to  the  generic  group  :  Cyclopsina, 
Milne-Edwards  ('38);  Glaucea,  Koch  ('38);  and  Cyclops, 
Nicolet  ('48). 

The  first  American  species  of  Diaptomus  recognizably 
described  was  D.  sanguineus  Forbes  ('76).  Later  Dr.  Forbes 
( '82a)  described  three  additional  species  of  this  genus  (sicilis, 
leptopus,  and  stagnalis),  and  two  new  genera  of  Centropagida 
(Epischura  and  Osphranticum),  with  a  single  species  of  each. 
Prof.  C.  L.  Herrick's  publications  on  the  group  began  in 
1877  and  those  of  Marsh  in  1891.  A  single  species  (Z>. 
kentuckyensis)  named  by  Chambers  in  1881  is  so  imperfectly 
described  that  its  recognition  is  apparently  impossible.  Since 
the  publication  of  Underwood's  "  List  of  the  described  Species 
of  Fresh-water  Crustacea  from  America  North  of  Mexico" 
('86)  the  number  of  recognized  North  American  species  of 
Diaptomus  has  increased  from  five  to  twenty-three. 

The  literature  of  the  genus  previous  to  1889  was  widely 
scattered  and  the  synonymy  greatly  complicated,  but  the 
comprehensive  and  careful  "lievision"  published  in  that 
year  by  de  Gucrne  and  Eichard  ('89b)  has  had  the  effect 
greatly  to  facilitate  its  study.  The  most  important  recent 
European  contributions  to  a  knowledge  of  the  Centropagidce 

9? 


98        Illinois  State  Laboratory  of  Natural  History. 


have  been  made  by  Claus,  Schmeil,  Poppe,  Imhof,  Zacharias, 
and  others,  in  Germany ;  by  Brady,  in  England ;  by  Nord- 
qvist,  in  Finland;  by  Sars,  in  Norway;  and  by  Lilljeborg  in 
Sweden,  the  latter  especially  having  described  a  number  of 
American  species.  Perhaps  the  finest  work  yet  published 
on  Copepoda  in  general  is  Giesbrecht's  monograph  on  the 
"  Pelagischen  Copepoden  des  Golfs  von  Neapel"  ('92),  the 
general  classification  of  which  is  followed  in  the  present- 
article. 

It  has  been  my  purpose  in  preparing  this  paper  to  do  for 
the  students  of  American  C  entropayidxe  a  service  similar  to 
that  which  de  Guerne  and  Richard  have  rendered  to  students 
of  this  group  as  distributed  throughout  the  world.  I  am 
under  especial  obligation  to  my  instructor,  Prof.  S.  A.  Forbes, 
to  whose  encouragement  and  aid  any  value  this  paper  may 
have  is  to  be  largely  attributed.  I  am  indebted  also  for 
specimens  or  other  favors  to  Dr.  Wilhelm  Lilljeborg,  of 
Upsala,  Sweden;  to  Dr.  Otto  Schmeil,  of  Magdeburg,  Ger- 
many; to  Herr  S.  A.  Poppe,  of  Vegesack,  Germany;  to  Prof. 
C.  Dwight  Marsh,  of  Ripon  College,  Wisconsin;  to  Prof.  L. 
S.  Ross,  of  Drake  University,  Des  Moines,  Iowa ;  to  Mr. 
Adolph  Hempel,  now  of  the  Museu  Paulista,  Sao  Paulo,  Bra- 
zil ;  to  Prof.  Frank  Smith,  of  the  University  of  Illinois  ;  to  Mr. 

C.  E.  Phillips,  of  Millington,  111. ;  and  to  my  friend  and  fellow 
student,  Mr.  E.  B.  Forbes.  I  have  also  to  call  attention  to 
the  fact  that  most  of  the  figures  accompanying  this  paper 
were  drawn  by  the  Artist  of  the  State  Laboratory,  Miss 
Lydia  M.  Hart. 

From  Dr.  Lilljeborg  I  received  specimens  of  Diaptomus 
signicauda,  IK  minutus,  I),  tryhomi,  D.  eiseni,  D.  francisca- 
nus,  Epischura  nevadensis,  and  E.  nordenski'oldi.  Prof.  Ross 
and  Mr.  Hempel  kindly  loaned  me  their  personal  collections, 
the  former  thus  furnishing  me  D.  siciloides,  D.  piscince,  and 

D.  clavipes  sp.  nov.,  and  the  latter,  D.  mississippiensis  and 
D.  albuquerquensis .  Prof.  Marsh  has  sent  me  slides  or  entire 
specimens  of  D.  ashlandi,  D.  mississippiensis,  and/),  reighardi. 
To  Dr.  Schmeil  I  owe  thanks  for  several  kind  letters,  for  the 
European  species  D.  gracilis,  D.  graciloides,  D.  castor,  D. 


North  American  Species  of  Diaptomus, 


99 


salinus,  D.  coemleus,  and  D.  zachariasi,  and  for  specimens 
of  Heterocope  and  Temorella, — all  of  which,  however,  arrived 
too  late  to  be  of  service  to  me  in  connection  with  this  paper. 
From  Herr  Poppe  I  received  the  following  species  :  D.  tyrrelli, 
D.  gibber,  D.  incongruens,  D.  deitersi,  I).  drieschi,  D.  zacha- 
riasi, and  Limnocalanus  sinensis. 

The  material  at  my  command  was  nearly  complete,  includ- 
ing all  but  two  of  the  known  North  American  forms  (D. 
novamexicanus  and  D.  birgei),  and  the  collection  of  the  liter- 
ature of  the  group  to  which  I  have  had  access  is  probably  as 
ample  as  that  to  be  found  in  any  library  in  this  country. 
In  compiling  the  bibliographical  list  appended  to  this  paper, 
Schmeil's  monograph  on  the  Ceniropagidm  ('96)  was  taken 
as  a  basis  and  was  especially  helpful,  while  a  great  deal  was 
also  gained  from  the  works  of  de  Guerne  and  Eichard. 

By  far  the  greater  part  of  the  collections  examined  are  the 
property  of  the  Illinois  State  Laboratory  of  Natural  History. 
They  represent  localities  distributed  over  the  entire  continent, 
from  Massachusetts  in  the  East  to  Oregon  in  the  West,  as  far 
south  as  Florida  and  as  far  north  as  Canada,  and  including  the 
following  states:  Massachusetts,  Florida,  Mississippi,  Ohio, 
Indiana,  Illinois,  Iowa,  Minnesota,  Michigan,  Wisconsin, 
Oregon,  Washington,  Montana,  Wyoming,  California,  Idaho, 
and  Nevada.  In  addition  to  the  above  I  have  examined 
specimens  from  Manitoba,  Newfoundland,  and  Greenland. 

The  localities  represented  by  these  collections  vary  widely 
in  character,  ranging  from  temporary  pools  on  the  Illinois 
prairies  to  Lakes  Michigan  and  Superior;  from  the  warm 
lakes  of  the  Florida  swamps  to  the  cold  mountain  lakes  of 
the  Eockies ;  and  from  the  small  head-water  streams  of  the 
Kaskaskia  to  the  sluggish  Illinois  and  the  mighty  Mississippi. 
The  collections  were  made  at  all  seasons  of  the  year  and  at 
nearly  all  times  of  the  day  and  night. 

Although  no  very  complete  data  for  any  single  locality  are  at 
hand,  it  is  found  that  in  ordinary  years  the  spring  and  early 
summer  are  the  most  favorable  seasons  for  collecting  in  our 
latitudes.  Individuals  are  found,  however,  at  all  times  ;  and 
in  some  cases  the  normal  habitat  is  a  lake  whose  waters  are 


100     Illinois  State  Laboratory  of  Natural  History. 

but  little  above  the  freezing  point,  or  even,  as  in  the  case  of 
I),  minutus,  water  flowing  from  the  foot  of  a  glacier.  Although 
this  would  seem  to  indicate  that  these  crustaceans  are  quite 
hardy,  I  have  repeatedly  found  that  in  jars  containing  living 
specimens  of  Cyclops,  Diaptomus,  and  Osphranticum,  those 
of  Diaptomus  were  the  first  to  succumb  to  unfavorable  con- 
ditions. 

The  genus  Diaptomus  is  the  most  cosmopolitan  of  its 
family,  species  having  been  reported  from  North  and  South 
America,  Europe,  Asia,  Africa,  and  Australia.  No  species, 
however,  is  known  to  be  common  to  the  mainlands  of  Europe 
and  of  America.  This  fact  is  the  more  remarkable  since 
almost  the  direct  opposite  is  true  of  the  companion  genus, 
Cyclops,  only  one  or  two  species  of  which  are,  so  far  as  known, 
peculiar  to  this  continent.  Even  D.  minutus,  which  is  found 
in  Oregon,  Illinois,  Wisconsin,  Minnesota,  Michigan,  New- 
foundland, Greenland,  and  Iceland,  has  not  as  yet  been  found 
in  northern  Europe  or  even  in  Great  Britain,  although  the 
expanse  of  salt  water  between  Iceland  and  Scotland  or  be- 
tween Iceland  and  Scandinavia  is  but  little  greater  than  that 
between  Greenland  and  the  mainland  of  North  America.  But 
few  species  of  this  genus  have  been  described  from  tropica] 
regions,  most  of  them  having  thus  far  been  found  in  the  north 
temperate  zone;  a  fact  to  be  attributed  doubtless  in  large 
measure  to  the  greater  attention  paid  to  zoological  studies  in 
these  northern  latitudes. 

In  this  paper  the  plan  followed  by  de  Guerne  and  Bichard 
in  their  "Bevision"  has  been  adopted,  separate  keys  being 
made  for  males  and  for  females.  When  females  are  so  nearly 
alike  as  in  I),  sicilis,  siciloides,  pallidus,  and  ashlandi,  it  is 
somewhat  difficult  to  find  distinguishing  characters,  and 
differences  not  usually  taken  into  account  must  be  seized 
upon.  The  males  are  much  more  easily  separated,  since  they 
offer  a  larger  number  of  peculiarities.  Giesbrecht  and 
Schmeil  have  paid  considerable  attention  to  the  armature  of 
the  entire  male  prehensile  antenna  instead  of  regarding  only 
that  of  the  last  three  segments,  and  in  one  or  two  cases  I 
have  done  the  same.     In  this  connection  a  fact  became 


North  American  Specie*  of  Diaptomus.  101 


evident  which  if  found  to  be  generally  true  will  necessitate  a 
slight  modification  of  the  description  of  the  family  Centro- 
pagidce.  I  refer  to  the  presence  of  a  sense-club  on  the  first 
segment  of  the  right  male  antenna.  In  his  monograph 
Giesbrecht  in  his  description  ('92,  p.  85),  says,  "Vordere 
antennen  ahnlich  wie  bei  den  Calaniden  gebaut."  On  another 
page  (42)  we  find  this  statement:  "The  normal  number  of 
processes  seems  to  be  three  for  each  segment,  a  proximal 
seta,  a  distal  seta,  and  a  sensory  structure  [testhetask],  but 
this  triad  is  never  complete  on  all  segments,  the  sense-club 
on  the  first  segment  being  always  wanting  and  the  sense-club 
and  proximal  seta  nearly  always  absent  on  the  twentieth  to 
the  twenty- fourth."  In  Diaptomus  stagnalis  and  D.  clavipes 
a  sense- club  is  present  on  the  first  segment.  The  statement 
that  the  inner  rami  of  the  fifth  pair  of  feet  are  "rudimentary, 
one-segmented,  or  lacking"  will  not  hold  in  many  species. 
Taking  only  those  forms  among  non-American  species  which 
were  described  in  de  Guerne  and  Richard  ('89b),  we  find  the 
following  with  tivo- segmented  inner  rami:  ]).  minis,  D. 
lobatus,  D.  theeli,  and  D.  glacialis,  Lilljeborg;  7).  coeruleus 
Fischer,  D.  gibber  Poppe,  and  D.  wierzejskii  Richard;  and 
at  least  three  American  species  have  the  inner  ramus  two- 
segmented —  D.  stagnalis  Forbes  distinctly,  and  7).  eiseni 
Lillj.  and  D.  albuquerq u crisis  Herrick  indistinctly  so. 

It  is  expected  that  the  keys  here  printed  will  be  used  in  con- 
nection with  the  descriptions  and  figures,  since  the  species 
vary  within  certain  limits,  and  no  hard  and  fast  description 
can  be  given  which  will  cover  the  peculiarities  of  every  indi- 
vidual of  a  species.  Local  varietal  differences  or  slight  vari- 
ations in  proportion  may  make  a  key  useless,  and  in  all 
cases  the  totality  of  characters  should  be  considered.  A 
glance  at  the  figures  will  indeed  often  be  found  more  helpful 
than  any  verbal  description. 

Following  the  usual  plan  of  specific  descriptions,  the  first 
paragraph,  referring  to  the  general  appearance  of  the  body, 
thorax,  abdomen,  and  furca  and  their  relative  proportions, 
applies  always  to  the  female  unless  especially  stated  other- 
wise. 


102      Illinois  State .  Laboratory  of  Natural  History. 


SYNOPSIS  OF  THE  RELATIONSHIPS  OF  THE  GENERA  Osphrailticitm , 

Limnocalanus,  Diaptomus,  and  Epischura, 
of  the  family  Centropagidcs. 

(Adapted  and  compiled  from  Giesbrecht  ('92),  and  from  manuscript 
of  Prof.  S.  A.  Forbes.) 

1  (19).    Division  of  body  into  cephalothorax  and  abdomen 

between  the  thoracic  segment  bearing  the  fifth  pair 
of  feet  and  the  segment  bearing  the  genital  apertures. 
In  the  male  the  fifth  pair  of  feet  assists  in  copulation. 
Abdomen  with  five  segments ;  without  appendages. 
Genital  organs  of  the  male  unsymmetrical.  Pulsating 
dorsal  vessel  generally  present.  Female  deposits  eggs 
singly  or  carries  them  with  her  in  single  sac  until  emer- 
gence of  the  nauplii.       Suborder  I.  GYMNOPLEA. 

2  (3).    Anterior  antennae  of  male  symmetrical  or  nearly  so, 

and  more  richly  provided  with  sense-clubs  [cesthetasks] 
than  those  of  the  female.  Fifth  pair  of  feet  of  female 
either  normal,  or  degenerate  to  complete  disappear- 
ance. Secondary  sexual  distinctions  of  male  not  con- 
fined to  peculiarities  in  the  structure  of  the  body,  the 
antennae,  the  fifth  pair  of  feet,  and  the  segmentation  of 
the  abdomen,  but  usually  present  in  the  cephalic 
appendages  and  sometimes  also  in  the -swimming  feet. 
Marine.  Tribe  I.  Amphaskandria. 

3(2).  Anterior  antennae  of  male  unsymmetrical.  Fifth  pair 
of  feet  in  the  female  either  normal  or  degenerated,  but 
never  absent.  Secondary  sexual  characters  of  male 
generally  confined  to  peculiarities  in  the  structure  of  the 
body,  the  antennae,  and  the  fifth  pair  of  feet.  Marine 
and  fresh-water.  Tribe  II.  Heterarthrandria. 

4  (18).  Kostrum  present.  Fourth  and  fifth  thoracic  seg- 
ments confluent. 

5(6).  Abdomen  of  female  1-3-segmented.  Antennae  16-24- 
jointed;  last  two  segments  always  confluent.  In  the 
male  the  fifth  pair  of  feet  rarely  with  a  rudimentary 
inner  ramus.  Antennae  with  segments  19-21  and 
sometimes  22-25  confluent.  Marine. 

Family  Pontellidte. 


North  American  Species  of  Diaptomus.  103 


6(5).  Abdomen  of  female  3-  or  4-segmented ;  sometimes 
unsymmetrical.  Antennae  never  with  less  than  24  seg- 
ments. In  the  male,  segments  19-21  and  generally  22 
and  23  are  confluent.  Abdomen  5-jointed ;  either  right 
or  left  antenna  prehensile.  The  fifth  pair  of  feet  are 
grasping  organs  and  both  always  present,  but  with 
inner  ramus  normal,  or  degenerate  to  complete  dis- 
appearance. Family  Centropagid.ze . 

7  (8).    Thorax  6-jointed.    All  the  feet  of  female  with  3-seg- 

mented  rami.  Abdomen  3- jointed.  Antennae  25- 
jointed,  segments  24  and  25  confluent.  Eight  male 
antenna  prehensile.  Outer,  ramus  of  left  fifth  foot 
2-jointed  ;  of  right,  subchelate. 

Subfamily  Centropagina. 

8  (7).    Thorax  5-jointed.    Fourth  and  fifth  thoracic  seg- 

ments confluent. 

9  (16,17.)    Abdomen  of  female  3-jointed,  sometimes  unsym- 

metrical. Antennae  23-  or  24-jointed.  Four  anterior 
pairs  of  feet  generally  with  3 -segmented  rami.  Fifth 
pair  of  feet  degenerate,  with  inner  ramus  wanting  or 
small  and  1- jointed,  outer  ramus  1-3  jointed.  Pre- 
hensile antenna  generally  the  right;  segments  19-21 
and  22  and  23  confluent.  Subfamily  Temorina. 

10  (11).    Furca  with  but  three  large  terminal  setae  to  each 

ramus.  Abdomen  of  male  unsymmetrical,  provided 
with  lateral  prehensile  apparatus.  Fifth  pair  of  legs 
of  female  uniramose,  3-jointed,  not  terminating  with 
a  long  spine.  Genus  Epischura. 

11  (10).    Furca  with  four  large  terminal  setae  to  each  ramus. 

12  (13).    Inner  ramus  of  first  pair  of  legs  2-jointed;  of  the 

following  three  pairs  3-jointed.  Fifth  pair  of  legs  in 
both  male  and  female  biramose,  inner  ramus  rudi- 
mentary. Genus  Diaptomus. 

13  (12).    Both  inner  and  outer  rami  of  the  first  four  pairs  of 

legs  3-jointed.  Fifth  pair  of  legs  in  both  sexes  biramose, 
those  of  the  female  differing  from  the  other  legs  only 
by  the  presence  of  a  strong  inner  hook  on  the  second 


104      Illinois  State  Laboratory  of  Natural  History. 

joint  of  the  outer  ramus ;  those  of  the  male  with  the 
inner  ramus  3 -jointed  and  provided  with  plumose 
hairs,  as  in  the  other  legs. 

14  (15).  Fifth  pair  of  legs  of  female  with  the  inner  hairs  of  the 

last  joint  of  the  outer  ramus  transformed  into  short 
thick  spines.  In  the  male,  outer  ramus  of  left  leg  of 
fifth  pair  with  two  joints  ;  outer  ramus  of  right  leg  with 
three.  Genus  Osphranticum. 

15  (14).    Fifth  pair  of  legs  of  female  with  the  inner  hairs  of 

the  last  joint  of  the  outer  ramus  long  and'  plumose. 
Fifth  pair  of  legs  of  male  with  both  outer  rami  2- jointed. 

Genus  Limnocalanus. 

16  (9,  17).    Abdomen  of   female   4-jointed,  symmetrical. 

Antennae  2 5 -jointed,  articles  24  and  25  not  confluent. 
Four  anterior  pairs  of  feet  generally  with  3 -segmented 
rami,  the  fifth  with  3-segmented  outer  and  2-  or  3-seg- 
mented  inner  ramus.  Male  antennas  with  segments 
19-21  and  21-23  confluent.  Fifth  pair  of  feet  sub- 
chelate;  the  right  with  2-,  the  left  with  3-segmented 
rami.  Subfamily  Leuckartiina. 

17  (9,16).    Abdomen  3- or  4-jointed,  not  always  symmetrical. 

Four  anterior  pairs  of  feet  with  3-jointed  rami.  Gen- 
erally the  left  antenna  of  the  male  geniculate.  Articles 
19-21,  22  and  23  (or  22-25),  and  1  and  2  confluent. 
Fifth  pair  of  legs  with  3-segmented  outer  and  1-3- 
segmented  inner  rami.  Chelae  undeveloped  or  want- 
ing. Subfamily  Heteroch^tina. 

18  (4).  Kostrum  wanting.  Fourth  and  fifth  thoracic  segments 

of  female  not  confluent.  Abdomen  3-segmented.  Male 
genital  opening  on  the  left ;  right  antenna  prehensile, 
segments  17  and  18,  and  19  and  20  confluent.  Inner 
rami  of  fifth  pair  of  feet  wanting ;  outer  ramus  of  left 
foot  4-segmented,  of  right  foot  3-segmented.  Marine. 

Family  Candacidje. 

19  (1).    Division  of  body  into  anterior  and  posterior  parts  in 

front  of  the  last  (fifth)  thoracic  segment.  This  bears, 
almost  without  exception,  a  more  or  less  rudimentary 


North  American  Sjiecies  of  Diaptomus.  105 


pair  of  feet,  which  in  the  male  never  assist  in 
copulation;  on  the  contrary,  the  male  attaches  the 
spermatophores  directly  to  the  vulva  of  the  female 
without  the  help  of  appendages.  Genital  organs  of 
the  male  generally  paired,  the  openings  always  sym- 
metrical. Pulsating  dorsal  vessel  almost  always 
absent.  The  female  carries  the  eggs  with  her,  gener- 
ally cemented  into  one  or  two  egg  sacs,  until  emer- 
gence of  the  young. 

Suborder  II.  PODOPLEA. 
Diaptomus  Westwood. 

Cyclops,  O.  F.  Muller,  1785. 
Monoculus,  Jurine,  '20. 
Diaptomus,  Westwood,  '36. 
Cyclopsina,  Milne-Edwards,  *38. 
Glaucea,  Koch,  '35-41 
Cyclops,  ISTicolet,  '48-'49. 

"  Cephalothorax  always  with  seven  segments,  of  which  the 
anterior  two,  indistinctly  confluent,  form  the  head.  The  last 
thoracic  segment  in  the  female  rather  large,  posteriorly  deeply 
emarginate  in  the  middle,  and  often  produced  laterally  on 
both  sides  into  a  biangulate  lamina.  Abdomen  short,  nar- 
rower than  the  thorax ;  in  female  of  four  segments  (caudal 
rami  included),  of  which  the  first  is  dilated  anteriorly  and 
very  often  armed  with  a  lateral  spine  on  each  side ;  in  male 
composed  of  six  obvious  segments  of  about  equal  width. 
Caudal  rami  with  five  uniarticulate  plumose  setae  and  with 
another  much  smaller,  more  slender  seta  within.  The  front 
provided  with  two  minute  tentaculiform  appendages.  The 
first  pair  of  antennae  composed  of  25  segments,  increasing 
slightly  in  length  toward  the  tip.  The  geniculate  articulation 
between  the  18th  and  19th  segments  of  the  right  male 
antenna ;  the  six  preceding  segments  swollen,  the  five  following 
sometimes  confluent  into  two  articles.  The  outer  ramus  of 
the  second  pair  of  antennas  7 -jointed,  longer  than  the  inner 
ramus,  the  last  article  longest  of  all  and  armed  with  very 
long  apical  setae;    setae  of  preceding  articles  short  and 


106      Illinois  .State  Laboratory  of  Natural  History. 

subequal.  Second  pair  of  maxillae  short  and  thick;  third 
pair  elongate,  directed  forward,  7 -segmented,  and  provided 
with  short  setae.  The  eight  anterior  swimming  feet  biramose, 
the  inner  ramus  of  the  first  pair  2-,  of  the  following  pairs  3 -seg- 
mented. The  last  pair  of  feet  different  from  the  rest,  5-seg- 
mented,  the  second  segment  armed  within  with  a  small 
appendage  or  rudiment  of  an  inner  ramus ;  in  the  female 
short,  equal,  the  last  segment  very  short  and  rudimentary, 
the  penultimate  always  produced  into  a  strong  hook  curved 
inward ;  in  the  male  the  right  foot  subchelate,  the  last  article 
formed  into  a  very  long  movable  hook.    Eye  single."* 

The  following  remarks  on  the  genus  are  from  de  Guerne 
and  Richard's  "  Revision  "  : 

"The  genus  Diaptomus,  known  at  a  very  early  date,  was 
for  a  long  time  confounded  with  Cyclops.  Clearly  distin- 
guished much  later,  it  contained  for  a  very  long  time  only  a 
few  recognized  species,  and  even  these  were  insufficiently 
defined.  Since  their  study  has  been  taken  up  with  more 
attention  other  forms  have  been  distinguished,  and  the  num- 
ber of  species  now  exceeds  forty,  and  further  explorations  will 
undoubtedly  bring  others  to  light,  t 

"  If  we  attempt  to  arrange  characters  in  the  order  of  their 
importance  from  a  systematic  point  of  view,  we  must  say 
in  the  beginning  that  they  are  furnished  almost  wholly  by 
the  males.  Except  in  certain  cases  the  isolated  females  are 
difficult  to  determine.  They  are,  however,  rarely  met  with 
alone,  and  collections  commonly  contain,  whatever  the  season, 
both  sexes  together. 

"  Among  the  characters  furnished  by  the  male,  the  greatest 
importance  must  be  assigned  to  those  of  the  fifth  pair  of  feet. 
The  length  of  the  inner  rami,  composed  of  one  or  two  seg- 
ments, varies  considerably  (minntus  to  castor).  As  for  the 
outer  rami,  the  last  article  of  the  left  foot  should  be  examined 
first.  It  sometimes  has  the  form  of  a  kind  of  forceps  and 
sometimes  terminates  in  a  sort  of  cushion  bearing  two  short 
obtuse  spines,  which  perhaps  represent  the  branches  of  the 

*  Translated  from  the  Latin  diagnosis  of  de  Guerne  and  Richard's  "Revision  des 
Calanides  d'Eau  Douce.''  pp.  9  and  10. 

fSixty-fivenow,  many  having  been  added  since  the  publication  of  the  '-Revision." 


North  American  Species  of  Diaptomus.  107 

forceps.  All  the  transitions  between  these  two  forms  may  be 
found  in  a  series  of  species.  Certain  articles  of  the  right 
ramus  may  also  bear  divers  characteristic  appendages. 
Finally,  the  terminal  claw  and  the  lateral  spine  of  the  last 
article  often  present  by  their  form  and  their  position  enough 
peculiarities  to  greatly  facilitate  the  determination. 

"  The  right  antenna  of  the  male  also  furnishes  some  good 
characters,  among  which  figure  in  the  first  rank  the  append- 
ages of  the  antepenultimate  article,  much  varied  as  to  form 
and  size  (D.  bacillifer,  wierzejskii,  coeruleus). 

"  Generally  speaking,  the  fifth  pair  of  feet  of  the  females 
furnish  the  most  important  specific  characters,  although  they 
do  not  have  the  same  technical  value  as  in  the  male.  At  the 
same  time  various  peculiarities  drawn  from  the  conformation 
of  the  last  cephalothoracic  and  of  the  first  abdominal  seg- 
ments and  from  the  length  of  the  antennae,  aid  greatly  in  the 
determination." 

KEY  TO  THE  NORTH  AMERICAN  SPECIES  OF  DiaptomUS,   BASED  ON 
THE  CHARACTERISTICS  OF  THE  MALE. 

1  (15).    Antepenultimate  article  of  right  antenna  without 

hook-like  process  at  tip. 

2  (3).    Antepenultimate  article  of  right  antenna  with  narrow 

hyaline  lamina.  Second  basal  segment  of  right  fifth 
foot  armed  at  the  inner  margin  with  two  hook-like  proc- 
esses, and  on  the  anterior  surface  at  the  apical 
margin,  with  a  hook-like  process  extending  beyond  the 
middle  of  the  first  segment  of  the  outer  ramus.  Inner 
ramus  extending  barely  beyond  the  middle  of  the. first 
segment  of  the  outer  ramus ;  heavily  spined  at  apex. 
Marginal  spine  below  the  middle  of  the  segment, 
near  the  apical  angle ;  short,  stout,  much  less  than 
half  as  long  as  the  segment.  Terminal  hook  very 
stout,  longer  than  preceding  segment.  Left  leg  ex- 
tending about  to  end  of  first  segment  of  outer  ramus 
of  right  leg;  second  basal  segment  tuberculate  on 
inner  margin.  Inner  ramus  very  long,  extending  about 
to  middle  of  last  segment  of  outer  ramus ;  incurved, 


108      Illinois*  State  Laboratory  of  Natural  History. 

tuberculate,  and  armed  at  apex  with  short,  blunt 
spines.  Last  segment  of  outer  ramus  armed  with  a 
short  blunt  spine  and  a  very  long  spinulose  one. 

clavipes. 

3  (2).    Antepenultimate  article  of   right   antenna  without 

hyaline  lamina. 

4  (5,10).    Inner  ramus  of  right  fifth  foot  not  reaching  end  of 

first  segment  of  outer  ramus  ;  sharply  pointed.  First 
segment  of  outer  ramus  with  hyaline  lamina.  Marginal 
spine  below  middle  of  segment ;  less  than  half  as  long 
as  segment.  Terminal  hook  longer  than  the  two  pre- 
ceding segments.  Left  leg  extending  slightly  beyond 
end  of  first  segment  of  outer  ramus  of  right  leg ;  inner 
ramus  reaching  slightly  beyond  end  of  first  segment  of 
outer  ramus,  indistinctly  2 -segmented,  apex  bluntly 
rounded.  tyrrelli. 

5  (4,10).   Inner  ramus  of  right  fifth  foot  reaching  end  of  first 

segment  of  outer  ramus. 

6  (7).    Inner  ramus  of  left  fifth  foot  extending  to  base  of 

second  segment  of  outer  ramus,  or  slightly  beyond. 
Marginal  spine  below  middle,  near  apical  angle ;  less 
than  half  as  long  as  segment.  Terminal  hook  at  least 
as  long  as  the  two  preceding  segments.  Left  leg  reach- 
ing about  to  middle  of  second  segment  of  outer  ramus  of 
right  leg.  Last  segment  of  outer  ramus  armed  with 
•forcipate  structure;  inner  digitiform  process  armed 
with  cushion  on  inner  margin.  pallidus. 

7  (6).     Inner  ramus  of  left  fifth  foot  reaching  to  middle  of 

second  segment  of  outer  ramus. 

8  (9).    Marginal  spine  of  right  leg  above  middle  of  segment, 

very  stout,  as  long  as  or  longer  than  segment.  Term- 
inal hook  almost  as  long  as  the  two  preceding  segments 
and  second  basal  segment  taken  together.  Inner  ramus 
as  long  as  first  segment  of  outer  ramus.  First  seg- 
ment of  outer  ramus  with  broad  hyaline  lamina  on 
inner  margin.  Left  leg  not  quite  reaching  middle  of 
second  segment  of  outer  ramus  of  right  leg.  birgei. 


North  American  Species  of  Diqptomus,  109 


9  (8).   Marginal  spine  of  right  leg  below  middle  of  segment ; 

slender,  less  than  half  as  long  as  segment.  Terminal 
hook  longer  than  the  two  preceding  segments,  a  sharp 
angle  dividing  it  approximately  into  halves.  Inner 
ramus  reaching  end  of  first  segment  of  outer  ramus ; 
apex  bluntly  rounded.  Left  leg  reaching  beyond  middle 
of  last  segment  of  outer  ramus  of  right  leg.  Last  seg- 
ment of  outer  ramus  ending  in  a  forcipate  structure ; 
outer  digitiform  process  stout,  armed  on  inner  margin 
near  tip  with  cushion-like  hairy  process.  reighardi. 

10  (4,  5).    Inner  ramus  of  right  fifth  foot  reaching  well 

beyond  end  of  first  segment  of  outer  ramus. 

11  (12).    Inner  ramus  of  left  fifth  foot  long,  extending  beyond 

middle  of  second  segment  of  outer  ramus ;  leg  itself 
(disregarding  terminal  spines)  not  reaching  end  of  first 
segment  of  outer  ramus.  Marginal  spine  of  right  leg 
inserted  below  middle  of  segment,  near  apical  angle ; 
much  less  than  half  as  long  as  segment.  Terminal 
hook  shorter  than  the  preceding  segment.  piscincc. 

12  (11).    Inner  ramus  of  left  fifth  foot  short,  not  extending 

beyond  middle  of  second  segment  of  outer  ramus. 

13  (14).   Inner  ramus  of  left  fifth  foot  not  reaching  to  middle  of 

second  segment  of  outer  ramus  ;  leg  itself  reaching  end 
of  second  segment  of  outer  ramus  of  right  leg.  Mar- 
ginal spine  below  middle  of  segment  near  apical  angle ; 
almost  as  long  as  segment.  Terminal  hook  longer 
than  the  preceding  segment.  Inner  ramus  of  right 
foot  extending  beyond  end  of  first  segment  of  outer 
ramus.  oregonensis. 

14  (13).    Inner  ramus  of  left  fifth  toot  reaching  middle  of  sec- 

ond segment  of  outer  ramus  ;  leg  itself  reaching  about 
to  middle  of  second  segment  of  outer  ramus  of  right  leg. 
Marginal  spine  below  middle  of  segment,  about  half  as 
long  as  segment.  Terminal  hook  longer  than  the  two 
preceding  segments.  Inner  ramus  of  right  foot  ex- 
tending to  middle  of  second  segment  of  outer  ramus. 

mississippiensis. 


110      Illinois  State  Laboratory  of  Natural  History. 

15  (1).    Antepenultimate  article  of  right  antenna  with  hook- 

like process  at  tip. 

16  (27).    Process  on  antepenultimate  article  as  long  as  or 

longer  than  penultimate  article. 

17  (20).    Process  curved. 

18  (19).    Inner  ramus  of  right  leg  alone  2-segmented,  extend- 

ing almost  to  middle  of  second  segment  of  outer  ramus. 
Marginal  spine  below  middle,  near  distal  angle, 
smooth,  about  half  as  long  as  segment.  Terminal  hook 
fully  as  long  as  the  two  preceding  segments  and  the 
second  basal  segment  taken  together.  Second  basal 
segment  not  dilated.  Left  leg  reaching  about  to  middle 
of  first  segment  of  outer  ramus  of  right  leg;  inner 
ramus  barely  reaching  middle  of  last  segment  of  outer 
ramus.  franciscanus. 

19  (18).    Inner  ramus  of  both  legs  2-segmented.  Marginal 

spine  below  middle,  near  apical  angle  ;  hairy,  almost  as 
long  as  segment.  Terminal  hook  longer  than  the  two 
preceding  segments,  but  not  as  long  as  those  and  the 
second  basal  segment  taken  together.  Second  basal 
segment  dilated  into  rugose  lamella.  Inner  ramus  of 
right  leg  extending  about  to  middle  of  second  segment 
of  outer  ramus.  Left  leg  extending  about  to  middle  of 
second  segment  of  outer  ramus  of  right  leg;  inner 
ramus  extending  beyond  middle  of  last  segment  of 
outer  ramus.  ciseni. 

20  (17).    Process  straight. 

21  (22).   Process  sharply  pointed.  Marginal  spine  below  mid- 

dle, about  half  as  long  as  segment.  Terminal  hook 
longer  than  the  two  preceding  segments.  Inner  ramus 
of  right  leg  extending  a  little  beyond  end  of  first  seg- 
ment of  outer  ramus.  Left  leg  reaching  slightly  beyond 
end  of  first  segment  of  outer  ramus  of  right  leg ;  last 
segment  of  outer  ramus  with  hairy  cushion  on  inner 
margin ;  inner  ramus  extending  almost  to  middle  of 
last  segment  of  outer  ramus.  .  shoshone. 

22  (21).    Process  blunt  or  swollen  at  tip. 


North  American  Species  of  Diaptomus.  Ill 


23  (24).    Inner  ramus  of  right  leg  rudimentary,  barely  sur- 

passing end  of  segment  from  which  it  arises.  Mar- 
ginal spine  about  at  middle  of  segment,  very  small. 
Terminal  hook  shorter  than  the  very  long  preceding 
segment.  Left  leg  extending  slightly  beyond  end  of 
first  segment  of  outer  ramus  of  right  leg ;  inner  ramus 
very  narrow,  extending  about  to  middle  of  second  seg- 
ment of  outer  ramus.  minutus. 

24  (23).    Inner  ramus  of  right  leg  not  rudimentary,  longer 

than  first  segment  of  outer  ramus. 

25  (26).    Marginal  spine  well  above  middle  of  segment,  about 

half  as  long  as  segment.  Terminal  hook 'longer  than  the 
two  preceding  segments.  Inner  ramus  of  right  leg  very 
narrow.  Left  leg  reaching  slightly  beyond  end  of  first 
segment  of  outer  ramus  of  right  leg ;  inner  ramus  extend- 
ing to  middle  of  last  segment  of  outer  ramus,  ashlandi. 

26  (25).    Marginal  spine  below  middle  of  segment,  less  than 

half  as  long  as  segment.  Terminal  hook  very  slender, 
longer  than  the  two  preceding  segments.  First  seg- 
ment of  outer  ramus  with  hyaline  lamina  at  inner  distal 
angle.  Left  leg  extending  about  to  middle  of  second 
segment  of  outer  ramus  of  right  leg ;  inner  ramus  ex- 
tending barely  to  middle  of  second  segment  of  outer 
ramus.  sic  His. 

27  (16).    Process  shorter  than  penultimate  article. 

28  (33).    Process  the  continuation  of  a  hyaline  lamina. 

29  (30).    Process  extending  at  least  to  middle  of  penultimate 

article.  Hyaline  lamina  extending  but  little  more  than 
the  distal  half  of  the  segment.  Marginal  spine  below 
middle  of  segment ;  shorter  than  segment.  Terminal 
hook  longer  than  the  two  preceding  segments  but  not 
as  long  as  those  and  the  second  basal  segment  together. 
Inner  ramus  of  right  leg  extending  slightly  beyond  end 
of  first  segment  of  outer  ramus.  Left  leg  extending 
slightly  beyond  end  of  first  segment  of  outer  ramus  of 
right  leg ;  inner  ramus  extending  about  to  middle  of 
last  segment  of  outer  ramus.  mvamexicanua. 


112      Illinois  State  Laboratory  of  Natural  History. 

30  (29).  Process  extending  very  slightly  beyond  end  of  article 

of  which  it  is  a  part.  Hyaline  lamina  extending  entire 
length  of  segment. 

31  (32).    Inner  ramus  of  right  leg  reaching  well  beyond  mid- 

dle of  the  very  long  first  segment  of  the  outer  ramus. 
Marginal  spine  below  middle,  near  apical  angle ;  less 
than  half  as  long  as  segment.  Terminal  hook  shorter 
than  the  preceding  segment.  Left  leg  (excluding  ter- 
minal spines)  reaching  about  to  middle  of  first  segment 
of  outer  ramus  of  right  leg.  Last  segment  of  outer 
ramus  terminated  by  two  spines ;  inner  ramus  reach- 
ing well  beyond  end  of  first  segment  of  outer  ramus, 
but  not  to  middle  of  last  segment.  leptopus. 

32  (31).    Inner  ramus  of  right  leg  rudimentary  (the  suture 

being  rarely  visible),  barely  reaching  the  end  of  the 
very  short  first  segment  of  the  outer  ramus.  Marginal 
spine  below  middle  of  segment,  less  than  half  as  long  as 
segment.  Terminal  hook  stout,  longer  than  the  pre- 
ceding segment.  Second  basal  segment  very  broad, 
armed  at  outer  distal  angle  with  a  process  about  as 
large  as  the  inner  "ramus."  Left  leg  very  short,  barely 
reaching  end  of  second  basal  segment  of  right  leg; 
inner  ramus  very  short,  extending  .barely  beyond  end 
of  first  segment  of  outer  ramus.  sanguineus. 

33  (28).    Process  not  the  continuation  of  a  hyaline  lamina. 

34  (41).    Process  straight. 

35  (36).    Process  serrate  on  outer  margin,  extending  beyond 

middle  of  penultimate  article.  Inner  ramus  of  right 
leg  very  broad  and  short,  extending  but  slightly  be- 
yond middle  of  first  segment  of  outer  ramus.  Margi- 
nal spine  above  middle  of  segment,  less  than  half  as 
long  as  segment.  Terminal  hook  longer  than  the  very 
long  preceding  segment.  Left  leg  very  short,  extend- 
ing barely  beyond  end  of  first  segment  of  outer  ramus 
of  right  leg.  First  basal  segment  of  both  legs  with 
long  slender  spine  on  posterior  surface.  trybomi. 
•36  (35).    Process  not  serrate. 


North  American  Species  of  Diaptomus. 


113 


37  (38).    Inner  ramus  of  right  leg  rudimentary,  extending  but 

slightly  beyond  the  end  of  the  segment  to  which  it  is 
attached.  Marginal  spine  below  middle  of  segment, 
slender,  fully  half  as  long  as  the  very  long  segment. 
Terminal  hook  shorter  than  the  preceding  segment. 
Left  leg  (disregarding  terminal  spines)  not  reaching  end 
of  first  segment  of  outer  ramus  of  right  leg.  Last  seg- 
ment with  two  spines  :  one  long,  slender,  outcurved ;  the 
other  short,  stout.  Inner  ramus  extending  almost  to 
end  of  last  segment  of  outer  ramus.  lintoni. 

38  (37).    Inner  ramus  of  right  leg  not  rudimentary,  extend- 

ing to  middle  of  first  segment  of  outer  ramus  or  beyond. 

39  (40),    Inner  ramus  of  right  leg  extending  about  to  middle 

of  first  segment  of  outer  ramus.  Marginal  spine  below 
middle,  about  half  as  long  as  segment.  Terminal 
hook  longer  than  the  preceding  segment.  Second  basal 
segment  with  hyaline  lamina  on  inner  margin.  Left 
leg  (disregarding  terminal  spines)  reaching  about  to 
middle  of  first  segment  of  outer  ramus  of  right  leg ; 
inner  ramus  reaching  end  of  first  segment  of  outer 
ramus,  corrugate  on  inner  margin.  stagnalis. 

40  (39).    Inner  ramus  of  right  leg  extending  beyond  the  end  of 

the  very  short  first  segment  of  outer  ramus.  Marginal 
spine  below  middle  of  segment,  stout,  longer  than 
segment.  Terminal  hook  very  long,  stout,  longer  than 
remainder  of  leg.  Left  leg  extending  beyond  end 
of  first  segment  of  outer  ramus  of  right  leg;  second 
segment  with  ciliate  lamina  on  inner  margin;  inner 
ramus  reaching  end  of  first  segment  of  outer  ramus. 

albuquerquensis. 

41  (34).    Process  curved. 

42  (43).    Process  small,  not  reaching  middle  of  penultimate 

article.  Marginal  spine  below  middle ;  rather  stout, 
less  than  a  third  the  length  of  segment.  Terminal  hook 
noticeably  longer  than  the  two  preceding  segments. 
First  segment  of  outer  ramus  with  hyaline  lamina  on 
inner  margin,  the  inner  apical  angle  of  which  is  not 


114     Illinois  State  Laboratory  of  Natural  History. 

produced.  Inner  ramus  of  right  leg  not  reaching  end 
of  first  segment  of  outer  ramus  ;  apex  bluntly  rounded. 
Left  leg  reaching  about  to  end  of  first  segment  of  outer 
ramus  of  right  leg ;  inner  ramus  reaching  middle  of  last 
segment  of  outer  ramus,  margins  sinuously  curved. 

siciloides. 

43  (42).  Process  stout,  reaching  to  middle  of  penultimate 
article  or  beyond.  Marginal  spine  below  middle  of  seg- 
ment, less  than  half  as  long  as  segment.  Terminal  hook 
not  much  if  any  longer  than  the  two  preceding  seg- 
ments. First  segment  of  outer  ramus  with  hyaline 
lamina  on  inner  margin,  which  is  much  produced  at 
the  outer  apical  angle.  Inner  ramus  of  right  leg  conical, 
not  reaching  end  of  first  segment  of  outer  ramus.  Left 
leg  reaching  to  tip  of  first  segment  of  outer  ramus  of 
right  leg.  Inner  ramus  extending  beyond  middle  of 
last  segment  of  outer  ramus ;  margins  parallel ;  armed 
on  outer  margin  near  base  with  small  hemispherical 
process.  signicauda. 

KEY  TO  THE  NORTH  AMERICAN  SPECIES  OF  DiaptomilS,  BASED  ON 
THE  CHARACTERISTICS  OF  THE  FEMALE. 

1  (18).    Inner  ramus  of  fifth  pair  of  legs  noticeably  shorter 

than  first  segment  of  outer  ramus. 

2  (10).    Outer  ramus  distinctly  or  indistinctly  3-segmentfd. 

3  (4,7).    Inner  ramus  distinctly  2-segmented,  the  first  seg- 

ment very  short  and  subquadrate  ;  barely  reaching  end 
of  first  segment  of  outer  ramus ;  armed  with  two  straight 
hairy  spines,  almost  as  long  as  the  ramus.  Second 
segment  of  outer  ramus  with  small  spine  near  base  of 
third  segment ;  spinose  on  both  margins.  Third  seg- 
ment armed  with  two  stout  spines,  the  inner  hairy, 
about  twice  as  long  as  the  outer,  which  is  about  as 
long  as  the  spine  on  the  preceding  segment.  Last 
thoracic  segment  strongly  produced.  First  abdominal 
segment  longer  than  remainder  of  abdomen,  greatly 
dilated,  armed  on  each  side  with  large  spine ;  second 
segment  shorter  than  third.    Furcal  rami  about  as 


North  American  Species  of  Diaptomus. 


115 


long  as  wide,  hairy  within.  Antennae  extending  barely 
to  base  of  abdomen.  stagnalis* 

4  (3,7).    Inner  ramus  indistinctly  2-segmented. 

5  (6).    Terminal  spines  of  inner  ramus  about  half  as  long  as 

ramus.  Second  segment  of  outer  ramus  armed  with  a 
single  spine.  Two  spines  on  the  third  segment ;  suture 
between  this  and  preceding  segment  indistinct.  Inner 
ramus  extending  beyond  middle  of  first  segment  of 
outer  ramus ;  armed  at  apex  with  two  long  spines. 
Third  segment  of  outer  ramus  armed  with  two  very 
large  stout  spines,  the  inner  hairy,  less  than  twice  as 
long  as  the  outer.  First  abdominal  segment  longer 
than  remainder  of  abdomen;  armed  anteriorly  with 
large  lateral  process.  Antennae  reaching  process  on 
first  abdominal  segment.  eiseni. 
.  6  (5).  Terminal  spines  of  inner  ramus  not  nearly  half  as  long 
as  ramus.  Second  segment  of  outer  ramus  with  a  spine. 
Inner  ramus  extending  slightly  beyond  middle  of  first 
segment  of  outer  ramus.  Third  segment  of  outer 
ramus  hairy  and  about  twice  as  long  as  the  inner,  which 
is  smooth.  First  abdominal  segment  longer  than  re- 
mainder of  abdomen,  armed  laterally  with  strong  spines. 
Antennae  extending  beyond  tips  of  furcal  setae. 

albuqjjberquensis, 

7  (3,4).    Inner  ramus  1-segmented. 

8  (9).    Terminal  spines  of  inner  ramus  smooth,  more  than 

half  as  long  as  ramus,  which  is  rounded  at  apex  and 
hairy.  Second  segment  of  outer  ramus  straight,  as 
long  as  or  longer  than  preceding  segment ;  armed  at 
base  of  third  segment  with  short  spine,  shorter  than 
either  of  the  two  on  third  segment.  Inner  spine  of 
third  segment  hairy,  about  twice  as  long  as  the  outer, 
which  is  smooth.  Both  spines  considerably  longer 
than  the  segment  itself.  Last  thoracic  segment  armed 
on  each  side  with  two  small  spines.  First  abdominal 
segment  shorter  than  remainder  of  abdomen,  dilated, 
armed  with  large  spines ;  second  segment  very  short. 


116     Illinois  State.  Laboratory  of  Natural  History. 

Third  segment  and  furcal  rami  about  equal.  Antenna? 
reaching  base  of  abdomen.  shoshone. 

9  (8).    Terminal  spines  of  inner  ramus  smooth,  not  nearly 

half  as  long  as  ramus,  which  is  hairy  at  apex  and  on 
inner  margin.  Second  segment  of  outer  ramus  curved, 
barely  as  long  as  preceding  segment ;  armed  at  base 
of  third  segment  with  an  inconspicuous  spine.  Third 
segment  armed  with  two  short  spines  but  slightly  longer 
than  the  segment.  Last  thoracic  segment  armed  with 
small  spines.  First  abdominal  segment  with  a  sharp 
spine  ;  longer  than  remainder  of  abdomen.  Antennae 
reaching  furcal  rami.  novamexicanus. 

10  (2).    Outer  ramus  2-segmented. 

11  (12).    Inner  rarnus  almost  rudimentary,  not  nearly  reach- 

ing the  middle  of  first  segment  of  outer  ramus.  Second 
segment  of  outer  ramus  considerably  shorter  than  first ; 
third  segment  represented  by  two  spines,  the  inner 
about  twice  as  long  as  the  outer.  Last  thoracic  seg- 
ment armed  on  each  side  with  small  spine.  First 
abdominal  segment  as  long  as  remainder  of  abdomen ; 
second  segment  very  short ;  third,  longer  than  furcal 
rami.    Antennae  reaching  slightly  beyond  furca. 

minutus. 

12  (11).    Inner  ramus  not  rudimentary,  reaching  beyond  the 

middle  of  first  segment  of  outer  ramus. 

13  (14).    Second  segment  of  outer  ramus  armed  with  a  short 

spine  ;  denticulate  within  and  without.  Third  segment 
represented  by  two  subequal  spines.  Inner  ramus  not 
nearly  reaching  end  of  first  segment  of  outer  ramus ; 
hairy  on  inner  margin ;  terminal  spines  fully  half  as 
long  as  segment.  First  abdominal  segment  dilated, 
about  equal  in  length  to  remainder  of  abdomen ;  sec- 
ond segment  and  furcal  rami  each  longer  than  third 
segment.  piscina. 

14  (13).    Second  segment  of  outer  ramus  not  armed  with  a 

spine. 


North  American  Species  of  Diaptomus. 


117 


14  (15).   Inner  ramus  armed  with  very  short  subequal  spines 

and  hairy  at  apex.  Second  segment  of  outer  ramus 
curved,  denticulate  on  inner  margin ;  third  segment 
represented  by  two  spines,  the  inner  the  longer  and 
about  half  as  long  as  the  second  segment.  Last  tho- 
racic segment  produced,  armed  with  two  large  spines  on 
each  side  ;  penultimate  thoracic  segment  produced  into 
dorsal  hump.  First  abdominal  segment  as  long  as 
remainder  of  abdomen,  armed  with  large  spine  on 
each  side ;  second  segment  shorter  than  the  third, 
which  is  about  equal  to  the  f ureal  rami.  Antennae 
extending  about  to  base  of  abdomen.  sanguineus. 

15  (14).    Inner  ramus  armed  with  long  conspicuous  spines. 

16  (17).    Second  segment  of  outer  ramus  straight,  about  as 

long  as  the  first,  armed  with  a  spine  at  base  of  third 
segment.  Inner  spine  of  third  segment  slightly  the 
longer.  Inner  ramus  hairy  at  apex ;  terminal  spines 
straight,  hairy,  about  a  third  as  long  as  the  ramus. 
Last  thoracic  segment  armed  on  each  side  with  a  spine. 
First  abdominal  segment  short,  unarmed.  Antennae 
extending  to  end  of  thorax.  leptopus. 

17  (16).    Second  segment  of  outer  ramus  straight,  slightly 

shorter  than  first ;  third  segment  represented  by  two 
subequal  spines.  Inner  ramus  barely  as  long  as  first 
segment  of  outer  ramus,  hairy  at  apex,  armed  with 
two  rather  long  spines.  Antennae  extending  to  end  of 
furca.  birgei. 

18  (1).    Inner  ramus  clearly  reaching  end  of  first  segment 

of  outer  ramus  or  beyond. 

19  (22).    Outer  ramus  3-segmentc(l. 

20  (21).    Third  segment  of  outer  ramus  small  but  distinct ;  in- 

ner of  the  two  spines  slightly  the  longer.  Second  seg- 
ment curved,  shorter  than  first;  denticulate  on  inner 
margin;  armed  with  small  spine  at  base  of  third  seg- 
ment. Terminal  spines  of  inner  ramus  very  long, 
almost  as  long  as  the  ramus.  Last  thoracic  segment 
armed  with  two   minute   spines.    First  abdominal 


118      Illinois'  State  Laboratory  of  Natural  History. 

segment  as  long  as  remainder  of  abdomen,  dilated, 
armed  with  small  spines  ;  second  segment  very  short ; 
third  segment  longer  than  f ureal  rami.  Antennae 
extending  to  furca.  franciscanus. 

21  (20).    Third  segment  of  outer  ramus  very  indistinct  or 

aborted ;  armed  with  two  short  subequal  spines.  Second 
segment  of  outer  ramus  about  as  long  as  the  first,  hairy 
within  and  without.  Inner  ramus  reaching  about  to 
end  of  first  segment  of  outer  ramus,  hairy,  armed  with 
two  long  hairy  subequal  spines.  First  abdominal  seg- 
ment shorter  than  remainder  of  abdomen,  dilated  but 
unarmed ;  second  segment  shorter  than  the  third, 
which  is  longer  than  the  furca.  Antennae  not  reaching 
end  of  furca.  piscina. 

22  (19).    Outer  ramus  2-segmented. 

23  (26).    Second  segment  of  outer  ramus  armed  with  a  spine 

in  addition  to  the  two  spines  representing  the  third 
•  segment. 

24  (25).    Terminal  spines  of  inner  ramus  hairy,  nearly  half  as 

long  as  ramus,  which  reaches  to  the  end  of  the  first 
segment  of  the  outer  ramus.  Second  segment  of  outer 
ramus  shorter  than  the  first,  slightly  curved,  denticulate 
within ;  third  segment  represented  by  two  spines,  the 
inner  hairy,  about  half  as  long  as  the  outer,  which  is 
smooth.  First  abdominal  segment  longer  than  re- 
mainder of  abdomen ;  second  segment  shorter  than 
third ;  the  third  longer  than  furca.  Antennas  reaching 
tip  of  f ureal  rami.  lintoni. 

25  (24).    Terminal  spines  of  inner  ramus  hairy,  not  nearly 

half  as  long  as  ramus,  which  is  hairy  at  the  apex.  Third 
segment  of  outer  ramus  represented  by  two  spines,  the 
inner  about  twice  as  long  as  the  outer.  Second  seg- 
ment armed  with  a  small  spine.  Last  thoracic  seg- 
ment greatly  produced  laterodorsally ;  armed  on  each 
side  with  two  small  spines.  First  abdominal  segment 
about  as  long  as  remainder  of  abdomen  and  armed 
with  two  large  spinose  processes ;   second  segment 


North  American  Sjiecies  of  Diaptomus. 


119 


shorter  than  third  and  about  equal  to  fureal  rami. 
Antennae  extending  beyond  base  of  furca  but  not  be- 
yond the  tip.  tyrrelli, 

26  (23).    Second  segment  of  outer  ramus  not  armed  with 

an  additional  spine. 

27  (32).    Second  segment  of  outer  ramus  longer  than  preced- 

ing segment. 

28  (29).    Outer  of  the  two  spines  representing  the  third  seg- 

ment of  outer  ramus  very  small  and  inconspicuous ; 
second  segment  shorter  than  the  first,  denticulate. 
Inner  ramus  reaching  slightly  beyond  end  of  first  seg- 
ment of  outer  ramus ;  hairy  on  outer  margin  and  at 
apex ;  armed  with  two  rather  long  subequal  spines. 
Last  thoracic  segment  produced  laterodorsally,  armed 
with  two  spines  on  each  side.  First  abdominal  seg- 
ment slightly  shorter  than  remainder  of  abdomen, 
dilated,  armed  on  each  side  with  a  large  spine  ;  second 
segment  shorter  than  third ;  third  segment  and  furca 
about  equal.    Antennae  reaching  beyond  tip  of  furca. 

clavipes. 

29  (28).    Outer  spine  rather  conspicuous. 

30  (31).    Terminal  spines  of  inner  ramus  smooth.  Inner 

ramus  reaching  end  of  first  segment  of  outer  ramus ; 
apex  hairy;  spines  small.  Second  segment  of  outer 
ramus  about  as  long  as  the  first,  denticulate,  point 
acute  ;  third  segment  represented  by  two  spines.  First 
abdominal  segment  as  long  as  remainder  of  abdomen, 
dilated,  armed  with  small  spines.;  second  segment 
shorter  than  third ;  third  about  equal  to  the  furca. 
Antennae  extending  to  tips  of  f ureal  setae. 

oregonensis, 

31  (30).    Terminal  spines  of  inner  ramus  hairy,  subequal. 

Second  segment  of  outer  ramus  about  equal  to  the 
first;  third  segment  represented  by  two  subequal 
spines.  Last  thoracic  segment  armed  on  each  side  with 
two  small  spines ;  the  penultimate  thoracic  segment 
with  a  small  hump.    First  abdominal  segment  slightly 


120      Illinois'  State  Laboratory  of  Natural  History. 

shorter  than  remainder  of  abdomen ;  second  segment 
shorter  than  third ;  third  segment  and  furca  about 
equal.  Antennae  extending  beyond  end  of  furca  but 
not  to  tips  of  furcal  setae.  signicauda. 

32  (27).    Second  segment  of  outer  ramus  shorter  than  preced-  " 

ing  segment. 

33  (34%    Last  thoracic  segment  with  a  large  dorsal  process, 

armed  with  two  spines,  one  minute.  First  abdominal 
segment  longer  than  remainder  of  abdomen,  with  short 
mucronate  process  anteriorly,  and  posteriorly  with 
large  triangular  process.  Second  segment  of  outer 
ramus  straight,  hairy;  third  segment  represented  by 
two  spines,  the  inner  about  twice  as  long  as  the  outer. 
Inner  ramus  noticeably  shorter  than  first  segment  of 
outer  ramus,  with  two  long  subequal  spines  at  the 
apex.    Antennae  barely  reaching  furca.  trybomi. 

34  (33).    Last  thoracic  segment  without  dorsal  process. 

35  (36).    First  abdominal  segment  longer  than  remainder  of 

abdomen,  dilated,  armed  with  small  spine  on  each  side  ; 
second  segment  very  short;  third  segment  shorter 
than  furcal  rami.  Second  segment  of  outer  ramus 
shorter  than  the  first ;  third  segment  represented  by 
two  spines  of  which  the  inner  is  the  longer.  Inner  ramus 
extending  beyond  end  of  first  segment  of  outer  ramus, 
hairy,  armed  with  two  smooth  subequal  spines.  An- 
tennae extending  just  beyond  furca.  ashlandi. 

36  (35).    First  abdominal  segment  about  equal  to  remainder 

of  abdomen. 

37  (38).    Second  abdominal  segment  very  much  shorter  than 

the  third.  Last  two  thoracic  segments  confluent ;  the 
last  one  armed  on  each  side  with  two  small  spines. 
First  abdominal  segment  with  large  spine  on  each  side  ; 
third  segment  longer  than  the  second  or  the  furca. 
Second  segment  of  outer  ramus  shorter  than  the  first ; 
third  segment  represented  by  two  small  spines,  the 
inner  about  twice  as  long  as  the  outer.    Inner  ramus 


North  American  Species  of  Diaptomus.  121 


hairy,  armed  with  two  small  spines.  Antennae  reach- 
ing slightly  beyond  end  of  furcal  rami.  siciloides. 

38  (37).    Second  abdominal  segment  slightly  shorter  or  at 

least  not  longer  than  the  third. 

39  (42).    Furca  longer  than  third  abdominal  segment. 

40  (41).    First  abdominal  segment  nearly  as  long  as  remain- 

der of  abdomen ;  dilated  laterally,  armed  with  one 
small  spine  on  each  side.  Second  segment  of  outer 
ramus  shorter  than  the  first ;  third  segment  represented 
by  two  spines,  the  inner  the  longer  and  pointed 
obliquely  outward.  Inner  ramus  reaching  end  of  first 
segment  of  outer  ramus ;  apex  hairy  and  armed  with 
two  spines.    Antennae  reaching  end  of  furcal  setae. 

reighardi. 

41  (40).    First  abdominal  segment  as  long  as  remainder  of 

abdomen;  dilated  laterally  but  unarmed.  Last  tho- 
racic segment  produced,  armed  with  one  small  spine  on 
each  side.  Head  partially  divided  by  a  suture.  Third 
segment  of  outer  ramus  represented  by  two  spines,  the 
inner  smooth,  about  twice  as  long  as  the  outer,  which 
is  delicately  hairy.  Inner  ramus  hairy,  armed  with 
two  long  subequal  spines.  Antennae  reaching  beyond 
end  of  furca.  pallidus. 

42  (39).    Furca  about  equal  to  third  abdominal  segment. 

43  (44).   First  abdominal  segment  about  as  long  as  remainder 

of  abdomen  and  armed  with  small  spines,  equal  on  the 
two  sides.  First  thoracic  segment  armed  with  small 
spine  on  each  side.  Second  segment  of  outer  ramus 
shorter  than  the  first ;  third  segment  represented  by 
two  spines,  the  inner  about  twice  as  long  as  the  outer. 
Inner  ramus  longer  than  first  segment  of  outer  ramus  ; 
hairy,  armed  with  two  spines,  the  inner  twice  as  long 
as  the  outer;  margins  sinuously  curved.  Antennae 
reaching  beyond  tip  of  furca.  sicilis. 

44  (43).    First  segment  of  abdomen  as  long  as  remainder  of 

abdomen;  armed  with  two  large  lateral  spines,  the 


122     Illinois  State  Laboratory  of  Natural  History. 

right  somewhat  the  longer.  First  two  thoracic  seg- 
ments equal,  together  about  half  as  long  as  entire 
thorax ;  last  segment  armed  with  two  small  spines. 
Second  segment  of  outer  ramus  very  broad,  especially 
at  the  base.  Inner  ramus  hairy  on  outer  margin  and 
at  tip,  which  is  armed  with  two  rather  long  slender 
spines.    Antennae  reaching  beyond  furca. 

missis  sippiensis. 

Diaptomus  sicilis  Forbes.    (PI.  XXI.,  Fig.  1-3.) 

Diaptomus  sicilis,  Forbes,  '82a,  p.  645,  PL  VIII.,  Fig.  9,  20. 
Diaptomus  pallidas  var.  sicilis,  Herrick,  '84,  p.  142,  PL  Q,  Fig.  18. 
Diaptomus  sicilis,  de  Guerne  et  Richard,  '89b,  p.  23,  Fig.  13,  14;  PL 
II.,  Fig.  13. 

Diaptomus  sicilis,  Forbes,  '90,  p.  702,  PL  I.,  Fig.  6. 
Diaptomus  sicilis,  Marsh,  '93,  p.  197,  PL  III.,  Fig.  8, 10. 

Body  slender,  widest  in  front  of  the  middle ;  suture  between 
head  and  thorax  distinct.  Last  two  thoracic  segments  con- 
fluent ;  the  last  one  produced  laterodorsally  and  armed  on  each 
side  with  one  or  two  small  spines ;  (in  the  male  unarmed.) 
Abdomen  long  and  narrow,  especially  in  the  male,  in  which 
the  first  segment  is  the  longest  and  slightly  the  broadest.  In 
the  female  (PI.  XXI.,  Fig.  3)  this  segment  is  fully  as  long  as 
the  remainder  of  the  abdomen,  dilated,  and  armed  on  each 
side  with  a  spine ;  last  three  segments  subequal.  Furcal 
rami  fully  twice  as  long  as  broad  and  hairy  within. 

Antennae  2 5 -segmented,  reaching  well  beyond  the  tips  of 
the  furcal  rami.  Male  geniculate  antenna  moderately  swollen 
beyond  the  twelfth  segment ;  first  two  segments  without 
special  armature ;  antepenultimate  segment  armed  with  nar- 
row spine-like  process  with  swollen  apex,  reaching  to  the 
middle  of  the  penultimate  segment;  segments  19,  20,  and 
21  confluent,  as  are  also  22  and  23. 

Fifth  pair  of  legs  in  the  male  (PL  XXL,  Fig.  1)  rather 
long  and  slender.  First  basal  segment  of  the  right  foot  with 
a  large  tubercle  on  the  posterior  surface  near  the  outer  mar- 
gin, bearing  a  minute  blunt  spine.  Second  basal  segment 
subquadrate,  about  one  and  a  half  times  as  long  as  broad. 
At  the  beginning  of  the  distal  third  of  its  outer  margin,  is  a 


North  American  Species  of  Diaptomus.  123 

small  cuticular  projection  bearing  a  delicate  hair.  First  seg- 
ment of  the  outer  ramus  subquadrate,  slightly  longer  than 
broad,  the  inner  distal  angle  provided  with  a  small  semi- 
elliptical  hyaline  lamina  arising  from  the  anterior  surface  of 
the  leg;  second  segment  slightly  arcuate,  the  two  margins 
parallel,  fully  twice  as  long  as  wide.  Marginal  spine  long 
and  slender,  slightly  curved,  about  half  as  long  as  the  seg- 
ment, and  inserted  at  the  beginning  of  the  distal  third.  Ter- 
minal hook  long,  slender,  and  regularly  curved ;  very  minutely 
denticulate  on  the  inner  margin. 

Inner  ramus  of  the  right  leg  either  one-  or  two- segmented, 
extending  beyond  the  end  of  the  first  segment  of  the  outer 
ramus  ;  minutely  hairy  at  the  tip.  . 

There  is  nothing  distinctive  about  the  basal  segments  of 
the  left  leg.  The  first  segment  of  the  outer  ramus  is  about 
one  and  a  half  times  as  long  as  broad ;  the  inner  distal  angle 
gradually  rounded  and  minutely  hairy.  The  second  segment 
is  narrow,  twice  as  long  as  broad  ;  armed  at  the  tip  with  two 
digitiform  processes  and  sometimes  with  a  much  smaller 
third  process  between  the  two.  This  segment  appears  very 
broad  and  fleshy  because  of  a  cushion-like  process  with  rugose 
surface  which  extends  beyond  the  inner  margin  of  the  seg- 
ment for  half  its  length.  The  other,  upper,  half  is  occupied 
by  a  minutely  hairy  semicircular  cushion. 

Inner  ramus  of  the  left  foot  either  one-  or  two-segmented,  ex- 
tending to  the  middle  of  the  last  segment  of  the  outer  ramus ; 
hairy  at  the  tip. 

Basal  segments  of  the  fifth  pair  of  feet  in  the  female  (PI. 
XXL,  Fig.  2)  not  characteristic.  The  usual  delicate  hair  is 
found  on  the  outer  margin  of  the  second  basal  segment. 
First  segment  of  outer  ramus  long  and  narrow,  more  than 
twice  as  long  as  broad.  Second  segment  almost  as  long  as 
the  first,  narrow,  tapering  to  a  fine  point,  delicately  spinose 
at  the  inner  margin.  Third  segment  wanting ;  represented 
by  two  spines,  both  sharp  and  slender,  the  inner  about  twice 
as  long  as  the  outer. 

Inner  ramus  of  fifth  leg  of  female  one-segmented,  project- 
ing slightly  beyond  the  end  of  the  first  segment  of  the  outer 


124     Illinois,  State  Laboratory  of  Natural  History. 

ramus,  the  proximal  four  fifths  of  uniform  width.  At  the 
beginning  of  the  distal  fifth  of  the  inner  margin  is  a  rather 
sharp  angle,  from  which  projects  a  long,  slender,  slightly 
curved  spine,  about  one  fifth  the  length  of  the  ramus. 
Beyond  this  the  ramus  tapers  to  a  blunt  point,  hairy  at  the 
apex.  Besides  the  spine  already  mentioned  there  is  a  smaller 
one,  only  about  half  as  long,  having  its  point  of  insertion 
very  near  and  slightly  above  the  first. 

Length  of  female  1.23-1.28  mm ;  of  male  1.00-1.18  mm. 

D.  sicilis  closely  resembles  both  D.  ashlandi  and  D. 
pallidas,  differing  from  the  latter,  however,  in  the  presence  of 
a  hook  on  the  right  male  antenna,  and  from  both  in  the  details 
of  structure  of  the  fifth  pair  of  feet  of  the  male. 

A  very  interesting  variation  was  noticed  in  the  inner  rami  of 
the  fifth  pair  of  feet  of  the  male.  In  specimens  taken  from 
Lake  Superior,  at  Marquette,  Mich.,  the  rami  were  sometimes 
both  one-segmented,  sometimes  both  were  two- segmented, 
and  at  other  times  one  ramus  was  two- segmented  while  the 
other  was  one-segmented.  Herrick  (Herrick  and  Turner,  595) 
states  that  all  his  specimens  had  one-segmented  rami;  also 
that  the  process  on  the  right  male  antenna  was  shorter  than 
described  by  Dr.  Forbes. 

Although  D.  sicilis  is  not  at  all  uncommon,  it  has  occurred 
less  frequently  in  the  collections  I  have  examined  than  have 
D.  siciloides  Lillj.,  D.  ashlandi  Marsh,  or  D.  oregonensis 
Lillj.  Marsh  ('93)  records  D.  sicilis  from  the  Great  Lakes 
and  from  Green  Lake,  Wis.,  it  being  the  common  pelagic 
species  in  1890  and  1891,  while  in  1892  not  a  single  specimen 
was  found  there  although  the  collections  were  made  at  the 
same  time  of  year.  The  type  was  described  (Forbes  '82a) 
from  Lake  Michigan  and  had  not  then  been  found  anywhere 
else.  In  1890  Dr.  Forbes  found  it  in  Lake  Michigamme,  in 
northern  Michigan,  as  well  as  in  Lake  Michigan.  His  variety 
imperfectus  is  D.  ashlandi  Marsh.  In  the  Yellowstone  Park 
collections  sicilis  was  found  in  considerable  quantities,  but 
as  both  D.  sicilis  and  D.  ashlandi  were  present,  it  would 
require  a  re-examination  of  the  material  to  determine  the 
distribution  of  the  two  species  in  that  locality. 


North  American  Species  of  Diaptomus.  125 


Diaptomus  piscinae  Forbes.    (PL  XXII.,  Fig.  1-4.) 

Diaptomus  piscince,  Forbes,  '93,  p.  253,  Pi.  XLL,  Fig.  22. 
Diaptomus  piscince,  Herrick  and  Turner,  '95,  p.  74,  PI.  V.,  Fig.  13. 

"A  species  of  medium  size  and  symmetrical  proportions, 
antennae  reaching  to  the  tip  of  the  abdomen,  cephalothorax 
broadest  about  the  middle,  with  four  distinct  sutures,  the 
posterior  lateral  angles  not  produced  but  armed  with  two 
distal  spines. 

'  'The  right  antenna  of  the  male  is  without  appendage  to 
the  antepenultimate  joint,  and  the  fifth  pair  of  legs  in  the 
same  sex  has  the  inner  ramus  well  developed  on  both  the 
right  and  left  sides.  The  usual  length  is  1.75  millimeters, 
the  transverse  diameter  0.45  millimeters  ;  the  abdomen  with 
furca  is  a  little  more  than  one  third  the.  length  of  the  cephalo- 
thorax. 

"  The  fifth  pair  of  legs  of  the  female  [PL  XXII.,  Fig.  2,  4]  is 
without  especially  marked  characters,  except  that  the  inner 
ramus,  which  reaches  to  the  tip  of  the  principal  segment  of 
the  outer,  is  provided  with  two  long,  stout,  equal  setae  more 
than  half  as  long  as  the  ramus  itself.  The  third  joint  of  the 
outer  ramus  is  aborted  and  bears  two  short,  stout  spines, 
and  the  joint  preceding  bears  a  slender  spine  outside  the 
base  of  the  last.  The  terminal  claw  of  this  joint  is  simple 
and  nearly  straight,  viewed  in  the  usual  position. 

"In  the  male  the  fifth  pair  of  legs  [PL  XXII.,  Fig.  1]  has 
a  considerable  resemblance  to  the  corresponding  append- 
ages of  J),  leptopus,  from  which,  however,  this  species  differs 
by  its  more  slender  form  and  by  the  absence  of  the  antennal 
hook.  The  peduncle  of  the  left  leg  is  quadrate  and  equal  in 
length  to  the  basal  segment  of  the  outer  ramus,  but  is  nearly 
twice  as  wide.  The  sides  of  this  latter  segment  are  parallel, 
the  inner  terminal  angle  is  broadly  rounded  and  minutely 
ciliate,  and  to  the  outer  terminal  angle  is  attached  the  second 
segment  of  the  ramus.  This  segment  is  a  trifle  shorter  than 
the  preceding  and  less  than  half  as  wide,  and  bears  at  its  tip 
a  stout,  blunt,  conical  spine,  whose  length  is  equal  to  that  of 
the  diameter  of  the  ramus,  and  within  this  a  long  flexible 


126     Illinois  State  Laboratory  of  Natural  History. 

hair  as  long  as  the  ramus  itself.  The  inner  ramus  of  this 
leg  is  very  long,  reaching  beyond  the  middle  of  the  terminal 
joint  of  the  outer  ramus.  It  is  slightly  concave  towards  this 
ramus  and  terminates  with  a  broadly  rounded  or  subtruncate, 
thickly  ciliate  end,  forming  an  acute  outer  angle  and  an 
obtuse  inner  one.  Seen  at  right  angles  to  this  view,  the  tip 
is  simply  obtusely  pointed. 

"  The  right  leg  of  the  male  is  without  remarkable  distin- 
guishing characters.  Basal  joint  of  the  outer  ramus  about 
two  thirds  as  long  as  the  peduncle  and  nearly  as  wide ;  sec- 
ond joint  slightly  longer  than  the  peduncle,  equal  to  the  first  in 
width ;  and  the  terminal  claw  sinuate  or  irregularly  curved. 
The  stout  seta  on  the  outer  margin  of  the  second  segment  of 
this  ramus  is  borne  at  about  a  quarter  the  length  of  the  seg- 
ment from  the  distal  end,  and  is  approximately  half  as  long 
as  the  segment  to  which  it  is  attached.  The  inner  ramus  is 
a  little  longer  than  the  basal  joint  of  the  outer.  It  is  not 
dilated  or  otherwise  modified,  but  terminates  bluntly,  bearing 
at  the  tip  a  covering  of  long  cilia. 

"The  right  antenna  of  the  male  is  without  notable  dis- 
tinctive characters.  The  antepenultimate  segment  is  as  long 
as  the  two  following  taken  together ;  the  fourth  from  the  tip 
bears  two  long  sword-like  spines  at  its  margin,  both  attached 
to  its  basal  fourth ;  the  expanded  segments  are  well  armed 
with  conical  spines,  straight  and  curved,  but  without  hooks. 

"  Small  lakelet  near  Gardiner,  Montana."* 

This  is  the  only  one  of  the  four  species  described  by  Dr. 
Forbes  ('93)  which  I  have  found  in  any  other  collections  than 
the  original  ones.  In  collections  loaned  me  by  Prof.  L.  S. 
Boss,  of  Drake  University,  Iowa,  made  by  him  at  Portage 
Slough,  Manitoba,  Canada,  in  June,  1895,  I  found  quite  a 
number  of  specimens  of  this  species,  which,  however,  exhibit 
a  number  of  peculiarities.  The  fifth  pair  of  legs  in  the 
female  are  stouter  and  the  inner  ramus  is  relatively  shorter 
than  in  the  Montana  specimens,  the  latter  not  reaching  to 
the  end  of  the  first  segment  of  the  outer  ramus  as  it  does  in  the 
type.     The  spines  on  the  inner  ramus  also  have  a  more 


■^Description  quoted  from  Forbes,  '93 


Nortli  American  Species  of  Diaptomus,  127 


distinct  and  broader  basal  portion  than  the  individuals  from 
Yellowstone  Park.  Both  the  inner  and  outer  margins  of  the 
second  segment  of  the  outer  ramus  are  hairy  in  Dr.  Forbes's 
specimens,  but  much  more  pronouncedly  so  in  the  specimens 
from  Portage  Slough. 

The  fifth  pair  of  feet  of  the  male  are  very  similar  to  the 
corresponding  appendages  of  D.  clavipes  sp.  nov.  and  D. 
leptopus  Forbes.  Dr.  Forbes  notes  the  differences  between  his 
species  (piscines  and  leptopus),  and  from  clavipes  both  may  be 
distinguished  at  a  glance  by  the  inner  rami  and  the  other 
peculiarities  mentioned  in  the  description  of  that  species.  A 
characteristic  of  D.  piscines,  and  one  which  was  neither  figured 
nor  described,  is  a  fin-shaped  process  on  the  middle  of  the 
anterior  surface  of  the  second  basal  segment  of  the  right  fifth 
foot  of  the  male.  This  is  armed  on  the  inner  margin  with  a 
row  of  bead-like  tubercles  and  is  more  distinct  in  the  Portage 
Slough  specimens.  This  process  corresponds  to  a  similar 
one  in  D.  clavipes.  The  lower  two  thirds  of  the  inner  margin 
of  this  segment  are  hairy,  and  at  the  end  of  the  proximal 
third  is  a  small  triangular  projection. 

The  terminal  hook  and  the  marginal  spine  of  the  outer  ramus 
of  the  right  male  foot  are  both  denticulate  on  the  lower  half  of 
the  inner  margin. 

In  the  "Preliminary  Eeport  on  the  Aquatic  Invertebrate 
Fauna  of  the  Yellowstone  National  Park,  Wyoming,  and  of 
the  Flathead  Region  of  Montana"  the  inner  ramus  of  the  right 
fifth  leg  of  the  male  (Fig.  22)  by  mistake  was  not  figured. 
The  description  was  correct  but  the  figure  did  not  correspond. 

The  first  and  second  segments  of  the  outer  ramus  of  the  left 
fifth  foot  of  the  male  are  hairy  on  the  inner  margin. 

The  length  of  the  Portage  Slough  specimens  is  as  follows : 
female,  2.11  mm;  male,  2.06  mm. 

Diaptomus  lintoni  Forbes.    (PL  XXVII.,  Fig.  1.) 

Diaptomus  lintoni,  Forbes,  '93,  p.  252,  PI.  XLII.,  Fig.  26-28. 
Diaptomus  lintoni,  Ilerrick  and  Turner,  "95,  p.  68,  P).  V.,  Fig.  12. 

"  A  large  red  species  occurring  commonly  with  D.  shoshone^ 
but  distinguishable  from  it  at  a  glance  by  its  different  shape, 


128      Illinois*  State  Laboratory  of  Natural  History. 

its  longer  antennae,  its  smaller  size,  and  by  characters  derived 
from  the  right  antenna  and  the  fifth  foot  of  the  male.  The 
thorax  is  symmetrically  elliptical  in  shape,  broadest  at  the 
middle.  The  posterior  angles  are  not  produced  or  bifid,  but 
are  each  armed  with  a  minute  spine.  The  first  segment  of 
the  abdomen  of  the  female  is  not  especially  produced,  but 
bears  at  its  broadest  part  a  minute  spine  on  each  side.  The 
abdomen  itself  is  very  short,  its  length  contained  about  three 
and  one  third  times  in  that  of  the  cephalothorax.  The 
antenna  of  the  female  is  long  and  slender,  25- jointed,  reach- 
ing a  little  beyond  the  tip  of  the  abdomen. 

"  The  fifth  pair  of  legs  in  this  sex  is  similar  to  those  of  D. 
shoshone,  but  much  smaller.  The  inner  ramus  is  not  jointed. 
It  is  longer  than  the  basal  joint  of  the  outer  ramus,  bears 
two  stout  plumose  setae  at  its  tip,  somewhat  shorter  than  the 
ramus  itself,  and  has  likewise  at  its  inner  tip  a  patch  of  small 
spines  or  fine  hairs.  The  second  segment  of  the  outer  ramus 
with  its  terminal  claw  is  two  thirds  as  long  again  as  the  pre- 
ceding segment,  the  breadth  of  the  latter  two  thirds  its  length. 
The  third  joint  is  indicated  by  a  single  long  stout  seta  and 
one  or  two  smaller  ones. 

"In  the  male  the  geniculate  antenna  is  relatively  rather 
slender,  its  last  two  joints  without  special  appendages,  its 
penultimate  with  a  slender  transparent  apical  process,  reach- 
ing about  to  the  middle  of  the  succeeding  segment,  acute  at 
tip,  but  neither  serrate  nor  emarginate.  Fifth  pair  of 
legs  in  the  male  [PI.  XXVII.,  Fig.  1]  usually  without  inter- 
nal ramus  to  the  right  leg,  but  this  ramus  sometimes  repre- 
sented by  a  small  rudiment.  The  limb  is  usually  slender 
and  its  terminal  claw  short.  The  basal  segment  of  the  outer 
ramus  is  nearly  as  long  as  the  adjacent  segment  of  the 
pedicel,  and  the  slender  second  segment  of  this  ramus  is 
fully  as  long.  Long  lateral  spine  borne  near  the  tip  of  this 
segment.  The  terminal  claw  is  about  two  thirds  as  long  as 
the  segment,  is  somewhat  abruptly  angulated  near  its  base 
and  slightly  recurved  at  the  tip.  The  inner  ramus  of  the  left 
leg  is  very  stout  and  long,  reaching  almost  to  the  tip  of  the 
outer  ramus,  is  slightly  curved  outwards  and  has  the  apex 


North  American  Species  of  Diaptomus.  129 


minutely  hairy.  The  basal  segment  of  the  outer  ramus  is 
thick,  two  thirds  as  broad  as  long,  somewhat  inflated  within, 
where  it  extends  downward  and  beyond  the  articulation  with 
the  second  segment  as  a  rounded  expansion  covered  with  ex- 
tremely fine  hairs.  Second  segment  of  this  ramus  longer 
than  first,  but  only  half  as  wide,  bearing  at  its  tip,  within,  a 
rather  small,  obliquely  projecting  cushion  covered  with  cilia, 
and  with  two  stout  terminal  spines,  one  short,  blunt,  straight, 
and  smooth,  the  other  curved  and  plumose,  its  length  about 
half  that  of  the  segment  to  which  it  is  attached. 

"The  total  length  of  this  species  is  about  2.5  millimeters, 
excluding  caudal  setae;  depth,  0.42  millimeters. 

"This  species  is  closely  related  to  D.  stagnalis,  Forbes, 
from  which  it  differs  conspicuously  by  its  smaller  size,  more 
symmetrical  cephalothorax,  without  prominent  or  bifid  angles, . 
and  longer  and  more  slender  antennae,  with  longer  and  more 
slender  appendage  to  the  antepenultimate  segment. 

"  In  the  fifth  legs  of  the  female  this  species  differs  from 
stagnalis  especially  with  respect  to  the  inner  ramus,  which  is 
larger  and  longer  than  in  the  other,  lacks  the  characteristic 
segmentation  of  stagnalis,  and  bears  at  its  tip  shorter  and 
broader  setae.  In  the  male  the  terminal  claw  of  the  outer 
ramus  of  the  right  fifth  leg  is  much  more  slender  than  in 
stagnalis,  and  the  inner  ramus  is  much  less  developed.  The 
left  leg  of  this  pair  is  different  in  a  number  of  details,  espe- 
cially in  the  length  and  strength  of  the  inner  ramus  and  the 
length  and  dissimilarity  of  the  setae  at  the  end  of  the  outer. 

"Common  in  lakes  and  pools  of  Yellowstone  Park."* 

This  species  is  one  of  the  three  American  forms  in  which 
the  inner  ramus  is  rudimentary  or  wanting,  the  other  two 
being  />.  sanguineus  Forbes  and  I>.  minutus  Lilljeborg.  It 
has  not  been  recorded  from  any  localities  outside  of  those  in 
which  it  was  originally  found. 


*  Description  quoted  from  Forbes,  '93. 


130     Illinois  State  Laboratory  of  Natural  History. 


Diaptomus  leptopus  Forbes. 

Cyclops  longicornis  (?),  Herrick,  '77,  p.  238,  Fig.  1. 

Diaptomus  kentuckyensis  (?),  Chambers,  '81,  p.  48,  PL  A,  Fig.  12-18; 

PI.  B,  Fig.  19-23. 
Diaptomus  leptopus,  Forbes,  '82a,  p.  646,  PI.  VIII.,  Fig.  17-19. 
Diaptomus  castor  (?),  Herrick,  '82,  p.  221,  PI.  I.,  Fig.  1-7;  PI.  II.,  Fig. 

12, 16. 

Diaptomus  longicornis  var.  leptopus,  Herrick,  '84,  p.  140. 

Diaptomus  leptopus,  de  Guerne  et  Richard,  '89b, p.  21,  PI.  II.,  Fig.  19; 

PI.  III.,  Fig.  9. 
Diaptomus  leptopus,  Marsh,  '93,  p.  195,  Pi.  III.,  Fig.  4,  5. 
Diaptomus  leptopus,  Herrick  and  Turner,  '95,  p.  64,  PI.  II.;  PI.  IX., 

Fig.  9. 

Body  long  and  slender,  widest  a  little  before  the  middle. 
Head  rather  noticeably  narrower  than  thorax,  suture  between 
them  distinct.  Fifth  and  sixth  thoracic  segments  confluent, 
the  last  produced  dorsally  on  each  side  into  a  triangular 
process  with  a  bluntly  rounded  apex  armed  with  a  single  blunt 
spine.  The  last  thoracic  segment  of  the  male  and  the  first 
abdominal  segment  of  both  sexes  unarmed.  First  abdominal 
segment  short,  a  little  more  than  half  as  long  as  the  succeed- 
ing segment.  Furcal  rami  about  one  and  a  half  times  as 
long  as  wide,  hairy  within. 

Antennae  2 5 -jointed,  extending  to  the  tip  of  the  furcal  rami. 
The  male  prehensile  antenna  rather  thickly  swollen,  the  first 
segment  without  armature,  the  other  segments  armed  as  fol- 
lows :  2,  with  a  short  seta  and  a  sense- club  ;  3,  short  seta  and 
sense- club  ;  4  and  6,  long  spine  ;  5  and  7,  long  seta  and  sense- 
club  ;  8,  long  spine  and  very  short  spine ;  9,  long  seta,  long 
spine,  and  sense-club ;  10  and  11,  process  and  long  spine; 
12,  long  spine,  very  short  spine,  and  sense-club  ;  13,  process, 
long  spine,  and  sense-club;  14,  long  seta,  long  spine,  and 
sense-club;  15,  process,  short  seta,  long  spine,  and  sense- 
club;  16,  process,  long  spine,  long  seta,  and  sense-club ;  17, 
process  and  short  thick  spine;  18,  process;  19,  20,  and  21 
(completely  ankylosed),  a  process,  a  long  seta,  and  a  very 
short  spine;  22  and  23  (completely  ankylosed),  a  narrow 
hyaline  lamina  produced  into  a  hook  which  extends  but  little 
beyond  the  end  of  the  segment,  and  two  long  setae ;  24,  two 


North.  American  Species  of  Diaptomus.  131 

long  setae;  and  25,  four  long  setae  and  a  sense-hair.  Some 
of  the  setae  on  the  last  segments  are  sparsely  hairy. 

Second  basal  segment  of  the  right  fifth  leg  of  the  male  sub- 
quadrate,  about  twice  as  long  as  wide ;  a  delicate  hair  at  the 
outer  margin  a  short  distance  above  the  distal  angle.  First 
segment  of  the  outer  ramus  somewhat  narrower  than  the 
second  basal  segment,  about  twice  as  long  as  wide;  sec- 
ond segment  very  long  and  narrow,  about  three  times  as 
long  as  wide.  Marginal  spine  slender,  about  one  third  the 
length  of  the  segment,  inserted  about  half  its  length  above 
the  outer  distal  angle  of  the  segment.  Terminal  hook  slender, 
regularly  curved,  about  as  long  as  the  preceding  segment ; 
distal  half  of  inner  margin  denticulate. 

Inner  ramus  of  right  fifth  foot  one- segmented,  reaching 
almost  to  the  end  of  the  first  segment  of  the  outer  ramus ; 
apex  broadly  triangular  and  minutely  hairy. 

Second  basal  segment  of  the  left  leg  of  the  male  subquad- 
rate,  slightly  broader  than  long ;  provided  with  a  delicate  hair 
a  short  distance  above  the  outer  apical  angle.  First  segment 
of  the  outer  ramus  irregular  in  form,  about  one  and  a  half 
times  as  long  as  broad,  with  two  rounded  protuberances,  the 
one  forming  the  inner  apical  angle  delicately  hairy.  Second 
segment  long  and  narrow,  almost  as  long  as  the  preceding 
segment  and  a  fourth  as  wide  as  long;  delicately  hairy 
at  the  inner  margin ;  armed  at  the  apex  with  a  short,  thick, 
blunt  digitiform  process,  and  a  long  curved  spine  as  long  as 
the  segment  itself  and  hairy  at  the  inner  margin. 

Inner  ramus  of  left  fifth  leg  long  and  narrow,  extending 
beyond  the  middle  of  the  second  segment  of  the  outer  ramus  ; 
margins  sinuous  ;  apex  triangular,  hairy. 

Second  basal  segment  of  the  fifth  pair  of  feet  in  the  female 
with  the  usual  marginal  hair.  First  segment  of  the  outer 
ramus  subquadrate,  about  twice  as  long  as  wide  ;  second  seg- 
ment narrow,  about  as  long  as  the  first,  tapering  to  a  rather 
blunt  point,  finely  dentate  on  the  inner  margin  and  with  a 
single  tooth  on  the  outer,  opposite  the  last  tooth  on  the  inner 
margin;  third  segment  small  but  distinct,  armed  with  two 
short  sharp  spines,  the  inner  slightly  longer  than  the  outer. 


132      Illinois  State  Laboratory  of  Natural  History. 

Just  without  these,  on  the  second  segment,  is  a  third  spine, 
shorter  than  either  of  the  other  two. 

Inner  ramus  of  fifth  leg  of  female  one-segmented,  extend- 
ing beyond  the  end  of  the  first  segment  of  the  outer  ramus; 
apex  hairy ;  armed  with  two  long  subequal  spines  hairy  on 
both  margins  and  about  a  third  the  length  of  the  ramus. 

Length  of  female  1.89  mm. ;  of  male  1.83  mm. 

Breadth  of  female  0.70  mm. ;  of  male  0.60  mm. 

The  numerous  published  figures  and  descriptions  of  this 
species  have  probably  made  it  well  known  to  all  students  of 
North  American  Centropagidce.  The  synonymy,  however,  is 
interesting.  In  the  Geological  and  Natural  History  Survey 
of  Minnesota,  Herrick  ('77,  p.  238)  describes  and  figures 
"A  New  Cyclops."  It  is  evident  at  a  glance  that  this  is  a 
Diaptomus,  but  of  what  species  cannot  be  determined.  In 
"Microscopic  Entomostraca  "  (Herrick,  '79,  p.  90)  he  refers 
to  this  "Cyclops"  and  says,  "In  the  Keport  of  the  Geological 
and  Natural  History  Survey  of  Minnesota  for  1878  it 
[Diaptomus  longicornis]  was  mentioned  and  a  figure  given, 
but  erroneously  called  Cyclops."  In  a  "Final  Report  on  the 
Crustacea  of  Minnesota  "  (Herrick,  '84,  p.  140)  he  makes  D. 
leptopus  Forbes  a  variety  of  D.  longicornis  Herrick,  estab- 
lishing a  second  variety,  similis  (Plate  Q,  Fig.  5-7).  In  his 
"  Synopsis  of  the  Entomostraca  of  Minnesota"  (Herrick  and 
Turner,  '95)  he  recognizes  D.  leptopus  Forbes  as  a  distinct 
species,  making  D.  longicornis  var.  leptopus  a  synonym ; 
although  in  this  same  work  D.  longicornis  var.  similis  Her- 
rick is  not  set  up  as  a  species,  neither  is  the  name  regarded 
as  a  synonym.  The  figures  (Herrick  '84,  PI.  Q,  Fig.  5-7)  are 
not  well  drawn,  but  it  is  not  likely  that  this  form  is  leptopus. 
J),  similis  is  referred  to  once  (Herrick  and  Turner  '95,  p.  58) 
in  connection  with  D.  franciscanus  Lilljeborg.  Diaptomus  ken- 
tuckyensis  Chambers  ('81)  is  also  quite  possibly  D.  leptopus, 
although  the  description  is  very  vague  and  the  figures  are 
inaccurate. 


North  American  Species  of  Diaptomus. 


133 


Diaptomus  sanguineus  Forbes.     (Pis.  XXIII.,  XXIV., 
and  XXV.) 

Diaptomus  sanguineus,  Forbes,  '76,  pp.  15, 1G,  23,  Fig.  24,  28-30. 

Diaptomus  sanguineus,  Forbes,  '82a,  p.  647,  PI.  VIII.,  Fig.  1-7, 13. 

Diaptomus  armatus(J),  Herrick,  '82,  p.  223,  Fig.  1,  a,  b. 

Diaptomus  armatusij),  Herrick,  '84,  p.  139. 

Diaptomus  sanguineus,  Herrick,  '84,  p.  138,  PI.  Q,  Fig.  12.. 

Diaptomus  minnetonka,  Herrick,  '84,  p.  138,  PI.  Q,  Fig.  8-10. 

Diaptomus  sanguineus,  de  Guerne  et  Richard,  '89b,  p.  20,  Fig.  9-11 ; 

PI.  IV.,  Fig.  24. 
Diaptomus  sanguineus,  Marsh,  '93,  p.  195,  PI.  III.,  Fig.  1-3. 

A  rather  large  species,  one  fourth  to  one  third  as  wide  as 
long.  The  cephalothorax  widens  gradually  to  the  third  seg- 
ment (being  broadest  at  the  suture  between  that  segment  and 
the  fourth),  then  narrows  less  gradually  to  the  abdomen.  In 
the  male  the  thorax  is  less  uniform  in  breadth  than  in  the 
female.  The  last  cephalothoracic  segment  is  greatly  pro- 
duced on  each  side  laterodorsally  and  bears  a  large  spine, 
slightly  swollen  at  the  base,  varying  in  length  from  that  of 
the  segment  to  one  fourth  its  length.  On  the  same  segment 
and  midway  between  the  outer  spine  and  the  abdomen  is 
another  broader  and  shorter  spine.  Both  of  these  spines  are 
slightly  curved.  In  the  female  (PI.  XXIV.,  Fig.  3)  they  are 
generally  quite  noticeably  larger  than  in  the  male.  On 
the  first  abdominal  segment  is  still  another  spine,  slightly 
outcurved  and  pointing  outward,  about  as  large  as  the  sec- 
ond of  the  spines  mentioned  above.  In  the  female  the 
penultimate  cephalothoracic  segment  bears  a  dorsal  hump  at 
its  anterior  margin  (PL  XXIV.,  Fig.  5,  6).  This  is  wanting 
in  the  male.  The  abdomen  is  produced  dorsally  and  ven- 
trally  at  the  anterior  part,  making  it  look  like  a  keel  (PI. 
XXIV.,  Fig.  1,  2),  the  keel  being  most  pronounced  on  the 
ventral  side.  The  egg-mass  is  large  and  elliptical,  with  the 
major  axis  transverse  to  the  body. 

Antennae  2 5 -segmented,  the  seventeenth  or  eighteenth  seg- 
ment reaching  about  to  the  base  of  the  abdomen.  The  right 
male  antenna  is  thickly  swollen  beyond  the  geniculate  joint. 
The  last  two  segments  have  no  special  armature,  but  the 
antepenultimate  one  (PI.  XXIII.,  Fig.  0-8)  is  armed  at  the 


134      Illinois  State  Laboratory  of  Natural  History. 


inner  distal  angle  with  a  short  thick  recurved  hook  with 
smooth  edges,  extending  but  little  beyond  the  joint.  This  is 
merely  the  continuation  of  the  hyaline  lamina  at  the  side  of 

the  segment. 

Second  basal  segment  of  the  right  fifth  leg  of  the  male 
(PI.  XXIII.,  Fig.  1-5),  seen  from  behind,  irregularly  trape- 
zoidal in  form,  very  broad  distally,  and  about  twice  as  long 
as  its  narrowest  part  is  wide.  On  the  outer  distal  angle  of 
this  segment  is  another  projection,  equal  to  or  greater  in 
length  than  the  inner  ramus.  This  also  shows  great  varia- 
tion, and  is  either  rounded  or  acute  or  even  acuminate  at 
the  apex.  First  and  second  segments  of  outer  ramus  sub- 
quadrate,  the  second  about  as  wide  as  the  first  and  about  two 
and  a  half  times  as  long.  About  a  third  the  length  of  the 
second  segment  from  its  base  is  a  considerable  contraction, 
the  width  here  being  about  half  the  width  of  the  broadest  part. 
Slightly  below  the  middle,  on  the  outer  margin,  is  a  spine, 
minutely  serrate  at  the  inner  edge.  This  is  generally  long 
and  straight,  about  half  the  length  of  the  segment,  but  varies, 
and  is  sometimes  shorter,  thicker,  curved,  and  less  than  one 
third  the  length  of  the  segment  (PI.  XXIV.,  Fig.  4  ;  PI.  XXV., 
Fig.  3-5).  Terminal  hook  rather  long  and  slender,  slightly 
and  sometimes  sinuously  curved,  about  one  and  a  fourth 
times  the  length  of  the  preceding  segment.  The  inner  margin 
is  serrate,  beginning  about  the  middle  of  the  hook  and  con- 
tinuing to  the  tip. 

Inner  ramus  of  the  right  fifth  foot  wanting,  a  peculiarity 
rarely  found  among  the  American  species  of  Diaptomus,  but 
approached  most  closely  by  D.  lintoni  Forbes  and  D.  minutus 
Lilljeborg,  in  which  the  ramus  is  very  small,  almost  rudi- 
mentary. The  ramus  is  represented  by  an  immovable  spine, 
minutely  spinose  at  the  tip.  This  is  greatly  diverse  in  shape 
and  sometimes  gives  indications  of  a  joint  (PI.  XXIII. ,  Fig. 
2),  as  if  a  case  of  ankylosis. 

Left  fifth  foot  of  the  male  biramose ;  second  basal  segment 
quadrate,  with  a  short  thick  spine  just  above  the  outer  distal 
angle.  Second  segment  of  outer  ramus  irregularly  subquad- 
rate,  about  two  thirds  as  wide  as  long,  provided  at  the  inner 


North  American  Species  of  Diaptomus.  135 

margin  with  a  cushion-like  protuberance  densely  covered  with 
minute  hairs.  This  segment  is  produced  into  two  spines, 
forming  a  forcipate  structure.  The  inner  spine  is  slightly 
shorter  than  the  main  part  of  the  segment,  thick,  incurved, 
and  movable,  and  armed  on  its  outer  margin  and  on  the  distal 
third  of  the  inner  one  with  minute  hairs.  The  outer  spine  is 
immovable,  ending  in  a  blunt  point,  and  its  curve  is  rather 
more  pronounced  than  that  of  the  inner  one. 

Inner  ramus  of  left  fifth  foot  one- segmented,  straight,  and 
armed  with  minute  hairs  at  the  apex.  It  is  about  three  times 
as  long  as  broad  and  reaches  beyond  the  middle  of  the  second 
segment  of  the  outer  ramus. 

First  basal  segment  of  the  fifth  foot  of  the  female  (PI.  XXV., 
Fig.  1,  2)  subquadrate,  slightly  longer  than  broad,  bearing 
a  short  thick  spine  near  the  outer  distal  angle.  The  distal 
segment  is  also  subquadrate  and  bears  the  usual  delicate  hair. 
Outer  ramus  two- jointed,  the  first  segment  oblong,  about 
twice  as  long  as  wide ;  second  segment  in  the  form  of  a  thick 
incurved  hook,  with  a  broad,  quadrate  basal  portion.  The 
hook  is  about  three  times  as  long  as  its  greatest  breadth,  the 
distal  fourth  of  the  inner  edge  armed  with  a  variable  number 
of  teeth  (8-15).  Third  segment  wanting,  represented  by  two 
spines ;  the  outer  short,  thick,  about  one  third  the  length  of 
the  segment ;  the  inner  rather  longer  and  more  slender,  sin- 
uously curved,  and  about  half  as  long  as  the  second  segment. 

Inner  ramus  of  fifth  foot  of  female  straight,  one-segmented, 
about  four  times  as  long  as  broad ;  armed  at  the  tip  with  two 
smooth  spines  of  almost  equal  length  and  but  slightly  curved. 
The  tip  of  the  ramus  is  delicately  hairy. 

Length  of  female  1.4-2.12  mm;  of  male  1.-2.  mm. 

Breadth  of  female  .4-.43  mm;  of  male  .3-.33  mm. 

The  synonymy  of  this  species  is  almost  as  complicated  as 
that  of  D.  leptopus.  First  described  by  Dr.  Forbes  (76),  it 
wTas  next  described  under  two  different  names  (D.  sanguineus 
and  D.  minnetonka)  by  Herrick  ('84).  I  am  also  led  to 
believe  very  strongly  that  Herrick's  D.  armatus  is  nothing 
but  a  variant  of  D.  sanguineus.  The  descriptions  and  figures 
(Herrick,  '82,  p.  223,  Fig.  1,  a  and  b)  seem  to  me  to  be 


136      Illinois^  State  Laboratory  of  Natural  History. 

without  specific  value.  The  following,  taken  from  Herrick  and 
Turner  '95a,  p.  72,  is  his  most  complete  description.  "It 
appears  to  be  allied  to  sanguineus.  The  antennae  are  said  to  be 
shorter  than  the  body,  the  caudal  stylets  narrow,  the  right 
male  antenna  has  a  hook  upon  its  antepenultimate  joint 
and  is  strongly  geniculate.  But  the  one  feature  which  may 
determine  the  species  is  the  existence  of  a  tooth  or  spur  near 
the  base  of  the  claw  of  the  right  fifth  foot  of  the  male." 

In  collections  from  Phelps  Lake,  Havana,  111.,  made  May 
18,  1894,  occurred  a  single  male  specimen  of  a  variant  of  D. 
sanguineus  which  might  easily  be  described  as  a  new  species 
if  the  spine  at  the  base  of  the  terminal  hook  were  taken  as 
the  one  specific  characteristic  to  which  all  others  must  be 
subordinated.  This  spine  is  straight  and  minutely  dentate 
on  both  margins.  In  all  other  respects,  except  a  slight  dif- 
ference in  the  length  of  the  terminal  hook,  the  specimen  is 
a  normal  D.  sanguineus.  The  fifth  pair  of  legs  is  shown  in 
PI.  XXV.,  Fig.  5.  The  occurrence  of  this  specimen,  taken  in 
connection  with  the  loose  descriptions  of  armatus,  has  led  me 
to  believe  in  the  identity  of  Herrick' s  species  and  this  variant. 

In  regard  to  D.  minnetonka,  Marsh  ('93)  points  out  that 
it  is  probably  but  a  variety  of  D.  sanguineus.  In  his  "Synopsis 
of  the  Entomostraca  of  Minnesota"  Herrick  says :  "We  are 
inclined  to  agree  with  Marsh  that  this  form  is  but  one  of  the 
many  variations  of  D.  sanguineus" ;  but  he  nevertheless  retains 
minnetonka  as  a  species  name  instead  of  making  it  a  synonym 
of  sanguineus. 

Diaptomus  sanguineus  occurs  in  early  spring  in  standing 
water  in  connection  with  D.  stagnalis  Forbes,  from  which  it 
may  be  distinguished  at  a  glance  by  the  difference  in  size, 
D.  stagnalis  being  about  twice  as  large  as  D.  sanguineus.  The 
latter  is  generally  a  deep  red,  but  D.  stagnalis  is  often  blue, 
with  abdomen  and  antennae  a  brilliant  red. 

The  theory  of  Herrick  (Herrick  and  Turner,  '95)  in  regard 
to  the  transition  of  forms,  "beginning  with  D.  stagnalis  and 
passing  through  several  varieties  to  D.  sanguineus  later  in 
the  season,"  will  not  hold  owing  to  the  fact  that  sexually 
mature  specimens  of  both  species  have  been  found  in  the 
same  pools  at  the  same  time. 


North  American  Species  of  Diaptomus.  137 


The  collection  from  which  the  variant  mentioned  above 
was  taken,  made  in  May,  1894,  consisted  almost  entirely  of 
7).  sanguineus.  Collections  from  the  same  waters  made  in 
July,  1896,  did  not  contain  a  single  individual  of  this  species, 
but  D.  skiloides  Lilljeborg  and  D.  pallidas  Herrick,  were 
present  in  immense  numbers. 

VARIATION  IN  D.  SANGUINEUS  FORBES.  " 

Plates  XXIII.,  XXIV.,  and  XXV.  were  prepared  before  the 
thesis  work  proper  was  undertaken  and  exhibit  the  results  of 
a  study  in  variation.  From  these  figures  it  will  at  once  be 
evident  that  D.  sanguineus  is  an  unusually  variable  species, 
and  without  the  intermediate  foi;ms  the  extremes  might 
almost  be  regarded  as  distinct.  The  specimens  examined 
were  all  from  the  collections  of  the  Biological  Station  at 
Havana,  so  that  the  variations  are  probably  not  so  great  as 
they  would  be  if  widely  separated  localities  were  represented. 
E  special  attention  was  given  to  variations  of  specific  char- 
acters, and  most  particularly  to  the  relative  proportions. 

The  second  basal  segment  of  the  right  leg  of  the  male, 
which  is  usually  very  broad,  in  fact  one  of  the  most  charac- 
teristic features  of  the  male,  is  shown  in  PI.  XXIII.,  Fig.  2,  to 
be  sometimes  of  very  ordinary  width,  the  other  extreme  being 
shown  in  PI.  XXIV.,  Fig.  4.  The  relative  position  and  length 
of  the  projection  on  the  outer  distal  angle  of  this  segment 
also  vary  a  great  deal,  the  extremes  noted  being  shown  in  PL 

XXIII.  ,  Fig.  1  and  2. 

The  marginal  spine  of  the  outer  ramus  of  the  right  fifth  leg, 
the  position,  relative  length,  and  characters  of  which  are  of 
specific  value  in  most  species,  lacks  such  value  almost  entirely 
in  7).  sanguineus.    The  extreme  variation  is  shown  in  PL 

XXIV.  ,  Fig.  4,  and  PL  XXV.,  Fig.  3. 

The  inner  ramus  of  the  right  fifth  leg,  though  always  very 
short,  varies  in  length  from  that  shown  in  PL  XXIV.,  Fig.  4,  to 
that  in  PL  XXIII.,  Fig.  2,  on  the  latter  of  which  is  also  shown 
a  rather  clearly  marked  suture  which  is  usually  wanting. 

The  variation  in  the  size  of  the  males  is  indicated  by  the 
drawings  of  the  fifth  pair  of  legs.  (See  PL  XXV.,  Fig.  3-5, 
and  PL  XXIV.,  Fig.  4.) 


138     Illinois  State  Laboratory  of  Natural  History. 


The  antepenultimate  article  of  the  prehensile  antenna  (PI. 

XXIII.  ,  Fig.  6-8)  is  not  so  variable,  but  still  quite  a  differ- 
ence may  be  noted  in  the  width  of  the  hyaline  plate  and  in 
the  relative  lengths  of  the  segments. 

In  the  female  the  variation  in  size  is  even  greater  than 
in  the  male,  the  fifth  legs  being  shown  in  PL  XXV.,  Fig.  1,2. 
The  variation  in  the  "hump"  of  the  female  is  slight  (PI. 

XXIV.  ,  Fig.  5,  6),  as  is  also  that  of  the  first  abdominal  seg- 
ment (PI.  XXIV.,  Fig.  1,  2). 

While  I  have  found  no  variation  whatever  in  the  color  of 
D.  sanguineus,  all  of  the  specimens  I  have  seen  alive  being  a 
bright  uniform  red,  as  were  also  those  examined  by  Dr. 
Forbes  (76),  and  by  Gissler  ('81),  Gissler  later  ('81a)  found 
individuals  colored  as  follows :  body  and  legs  bluish,  an- 
tennae and  furca  red,  and  abdomen  yellow.  Herrick  says 
in  the  description  of  D.  minnetonka  (Herrick  and  Turner,  '95), 
which  is  a  synonym  of  D.  sanguineus,  "color  dark."  In  the 
same  work,  in  his  description  of  D.  sanguineus,  he  says 
"brilliantly  colored."  According  to  my  observation  color  is 
of  no  certain  specific  value  in  Diaptomus,  but  it  may  be  that 
there  are  definite  seasonal  variations — a  subject  which  I  have 
not  investigated. 

Diaptomus  stagnalis  Forbes.    (PI.  XXVIIL,  Fig.  2.) 

Diaptomus  stagnalis,  Forbes.  'S2a,p.  646,P1.  VIII.,  Fig.  8, 10-12, 14. 
Diaptomus  giganteus,  Herrick,  '82,  p.  222,  PI.  II.,  Fig.  3, 11 , 15. 
Diaptomus  stagnalis,  Herrick,  '84,  p.  139,  PI.  Q,  Fig.  11, 13. 
Diaptomus  stagnalis,  de  Guerne  et  Kichard,'89b,  p.  23,  PI.  IV.,  Fig.  14. 

Head  distinct  from  thorax ;  fifth  and  sixth  thoracic  seg- 
ments confluent.  Lateral  angles  of  last  thoracic  segment 
strongly  produced  backward,  each  angle  bilobed,  the  outer 
lobe  about  twice  as  large  as  the  inner ;  (in  the  male  this  seg- 
ment is  salient.)  Abdomen  peculiar  in  that  there  is  a  sudden 
narrowing  at  the  beginning  of  the  third  segment.  First 
abdominal  segment  armed  with  a  large  spine  on  each  side 
(in  the  male  unarmed) ;  second  and  third  segments  of  the 
abdomen  subequal,  about  twice  as  wide  as  long.  Furcal 
rami  subquadrate,  hairy  within.    Furcal  setae  rather  short, 


North  American  Species  of  Diaptomus.  139 

densely  plumose.  There  is  but  little  difference  in  the  length 
of  the  abdominal  segments  of  the  male. 

Antennae  2 5 -segmented,  reaching  to  the  middle  of  the 
abdomen.  Prehensile  antenna  of  the  male  (PI.  XXVIII., 
Fig.  2)  thickly  swollen  anterior  to  the  twelfth  article,  with 
armature  as  follows :  segments  1  and  5,  long  spine  and 
sense-club;  2,  three  long  spines  and  sense-club;  3,  short 
seta;  4  and  6,  long  spine;  7,  short  seta  and  sense-club;  8 
and  12,  long  spine  and  short  spine;  9,  long  spine,  short 
seta,  and  sense-club;  10,  11,  13,  and  17,  process  and 
long  spine;  14  and  16,  long  spine,  short  seta,  and  sense- 
club  ;  15,  process,  two  long  spines,  and  sense-club  ;  18,  proc- 
ess; 19,  20,  and  21  (ankylosed,  with  the  sutures  indistinctly 
indicated),  two  processes,  a  stunted  spine,  and  a  long  seta ; 
22  and  23  (ankylosed),  a  broad  hook-like  process  not  reach- 
ing the  end  of  the  penultimate  segment,  and  four  setae;  24, 
two  setae;  and  25,  four  setae,  a  sense-hair,  and  a  sense-club. 

Second  basal  segment  of  the  right  fifth  foot  of  the  male 
subquadrate,  about  twice  as  long  as  wide ;  on  the  posterior 
surface  a  large  smooth  hyaline  lamina  occupying  about  a 
third  of  the  inner  margin  near  the  middle,  and  near  the  outer 
distal  angle  a  minute  cuticular  process  bearing  a  delicate 
hair.  First  segment  of  the  outer  ramus  almost  three  times 
as  long  as  broad ;  second  segment  about  as  long  as  the  first 
and  for  about  the  proximal  third  nearly  as  wide,  but  beyond 
this  considerably  broader.  Marginal  spine  near  the  outer 
distal  angle ;  straight,  very  strong  and  thick,  little  less  than 
half  as  long  as  the  segment.  Terminal  hook  rather  short 
and  very  stout,  irregularly  curved,  heavily  and  closely  den- 
ticulate at  the  distal  half  of  the  inner  margin. 

Inner  ramus  of  the  right  fifth  leg  spatulate,  not  nearly 
reaching  the  middle  of  the  first  segment  of  the  outer  ramus ; 
apex  rounded,  armed  with  a  few  strong  spines. 

Second  basal  segment  of  the  left  fifth  foot  armed  at  the 
outer  margin,  a  short  distance  above  the  distal  angle,  with  a 
short,  thick,  pointed  spine.  First  segment  of  the  outer  ramus 
about  three  times  as  long  as  wide,  armed  at  the  distal  third 
of  the  inner  margin  with  a  few  strong  hairs.    Second  segment 


140     Illinois  State  Laboratory  of  Natural  History. 

about  half  as  long  as  the  first,  having  on  the  inner  margin 
two  cushion-like  processes  (the  upper,  smaller  one  hairy,  and 
the  lower  densely  tuberculate),  and  being  armed  at  the  tip 
with  two  processes  forming  a  forcipate  structure,  the  outer 
broad,  plowshare-shaped,  the  inner  a  long  and  narrow  spine, 
hairy  within. 

Inner  ramus  of  left  fifth  foot  one- segmented,  of  the  same 
width  throughout,  with  a  broadly  rounded  tip ;  inner  margin 

rugose. 

Second  basal  segment  of  the  fifth  foot  of  the  female  with 
the  usual  delicate  hair  at  the  outer  margin.  First  segment 
of  outer  ramus  short  and  broad.  Second  segment  large, 
about  one  and  a  half  times  as  long  as  the  first,  armed  on  the 
middle  third  of  the  inner  margin  with  seven  or  eight  very 
large,  strong,  pointed  spines,  and  on  the  outer  margin  and 
opposite  the  upper  spines  of  the  inner  margin  with  three  or 
four  spines.  Third  segment  distinct,  armed  with  two  spines, 
the  outer  one  short,  thick,  sharp,  smooth,  the  inner  one  about 
twice  as  long  and  armed  with  a  few  rather  strong  spinules. 
Just  without  these  spines,  on  the  second  segment,  is  a  shorter, 
smooth  spine. 

Inner  ramus  of  the  fifth  foot  of  the  female  distinctly  two- 
segmented,  the  first  segment  subquadrate,  the  second  as  wide 
as  the  first  and  nearly  twice  as  long,  and  armed  at  the  tip 
with  two  thick  heavy  spines  reaching  to  the  end  of  the  second 
segment  of  the  outer  ramus.  These  spines  are  armed  with 
heavy  spinules.  Disregarding  the  spines,  the  ramus  reaches 
just  to  the  end  of  the  first  segment  of  the  outer  ramus. 

Length  of  female  4.0-4.5  mm. ;  of  male  3.5-4  mm. 

This  Diaptomus  is  the  largest  of  the  American  species  and 
a  very  beautiful  one.  Dr.  Forbes  states  in  his  original  des- 
cription ('82a)  that  "all  were  red  throughout."  Specimens 
taken  in  April,  1897,  from  ponds  south  of  Urbana,  111.,  when 
they  were  in  the  height  of  sexual  activity,  were  colored  as 
follows:  thorax  and  anterior  appendages  (all-  but  the  first 
pair  of  antennae)  blue ;  first  pair  of  antennae,  fifth  pair  of 
legs  (in  the  male),  and  abdomen  red.  In  the  female  all  the 
legs  were  blue.  J 


North  American  Species  of  Diaptomus.  141 


The  pool  from  which  they  were  taken  was  particularly  rich 
in  decaying  vegetable  material  and  received  the  drainage  of  a 
pasture  in  which  cattle  and  horses  were  allowed  to  graze. 
The  water  literally  swarmed  with  Volvox;  and  Diaptomus, 
Cyclops,  and  insect  larvae  were  very  abundant.  The  food  sup- 
ply was  practically  inexhaustible  and  the  specimens  taken 
were  unusually  large. 

Diaptomus  shoshone  Forbes.    (PI.  XXVI.,  Fig.  1-3.) 

Diaptomus  shoshone,  Forbes,  '93,  p.  251,  PI.  XLIL,  Fig.  23-25. 
Diaptomus  shoshone,  Herriek  and  Turner,  '95,  p.  01,  PL  V.,  Fig.  11. 

"A  very  large  and  robust  species.  Thorax  broadest  in 
front,  across  the  maxillae,  tapering  gradually,  with  little  con- 
vexity, to  the  posterior  third.  In  the  female  the  angle  of  the 
last  segment  is  bifid,  both  projecting  points  being  minutely 
spinose  at  tip.  The  first  segment  of  the  abdomen  (PI.  XXVI., 
Fig.  1)  is  laterally  expanded,  the  expansion  of  the  left  side 
with  a  minute  spine  at  the  apex,  behind,  that  on  the  right 
produced  at  the  same  point  into  a  small,  prominent,  rounded 
tubercle,  0.03  millimeter  in  length,  about  as  broad  as  long, 
making  this  first  segment  somewhat  unsymmetrical.  This  is 
not  merely  a  modified  cuticular  appendage,  but  is  penetrated 
by  the  hypodermis.  Egg-mass  very  large,  obovate  (narrowest 
forward) . 

"Eight  antenna  of  male  robust,  the  last  two  joints  without 
special  appendages,  antepenultimate  with  a  very  long  inartic- 
ulate process  at  its  outer  apex,  extending  beyond  the  tip  of 
the  penultimate  and  to  the  middle  of  the  last  segment.  The 
margins  of  this  process  are  smooth,  but  it  is  broad  and 
emarginate  at  the  tip. 

"  The  fifth  pair  of  legs  in  the  male  resemble  the  correspond- 
ing appendages  of  Diaptomus  staghalis,  but  differ  notably  in 
detail.  The  left  ramus  of  the  right  leg  is  borne  at  the  inner 
terminal  angle  of  the  second  joint ;  is  longer  than  the  joint 
following ;  is  armed  at  the  apex  with  a  few  small  acute  spines  ; 
and  bears  upon  its  outer  margin,  near  the  tip,  a  broad  fas- 
cicle of  delicate  hairs.  The  basal  joint  of  the  outer  ramus  is 
two  thirds  the  length  of  the  second  joint  of  the  peduncle, 


142      Illinois  State  Laboratory  of  Natural  History. 

and  without  hairs  or  spines  of  any  description.  The  second 
joint  of  this  ramus  is  about  equal  in  length  to  the  second 
joint  of  the  peduncle,  and  bears  on  its  outer  margin,  close  to 
the  tip,  the  usual  stout  seta,  which  is  two  thirds  as  long  as 
the  joint  to  which  it  is  attached.  The  terminal  claw  is  not 
regularly  curved,  but  is  nearly  straight  for  the  basal  three 
fourths.  The  left  leg  is  biramose,  the  inner  ramus  straight, 
slender,  extending  about  to  the  middle  of  the  second  joint  of 
the  outer,  and  armed  at  its  tip.  The  second  joint  of  this 
ramus  is  as  long  as  the  first,  if  measured  from  the  tip  of  the 
apical  spine.  This  spine,  seen  from  behind,  is  stout,  conical, 
rather  blunt,  and  has  opposed  to  it  within,  projecting  from  the 
inner  angle  of  the  segment,  a  stout,  curved  seta,  slightly 
plumose  on  its  distal  half.  Between  these,  but  more  closely 
applied  to  the  outer  spine,  is  a  hemispherical  cushion-like 
elevation,  set  with  small,  short  spinules.  On  the  basal  half 
of  the  inner  margin  of  this  terminal  segment  is  also  a  much 
larger  hemispherical  cushion,  but  with  longer  and  more  slen- 
der hairs,  while  the  terminal  half  of  the  inner  margin  of  the 
segment  preceding  is  also  moderately  inflated  and  covered 
with  delicate  hairs. 

"The  antennae  of  the  female  are  25-jointed,  as  usual, 
and  reach  to  the  base  of  the  abdomen.  The  legs  of  the  fifth 
pair  (PI.  XXVI.,  Fig.  2)  closely  resemble  those  of  stagnalis, 
but  have  the  terminal  setae  of  the  inner  rami  much  less  devel- 
oped. This  ramus  is  a  little  shorter  than  the  basal  joint  of 
the  outer  ramus,  and  of  about  half  its  diameter.  It  bears  at 
its  tip  two  stout  setae  equaling  the  ramus  itself  in  length,  plu- 
mose under  a  high  power,  and  has,  in  addition,  at  its  inner 
tip  and  on  the  inner  margin  adjacent,  a  patch  of  delicate 
hairs  and  spines.  The  second  joint  of  the  outer  ramus  is  as 
long  as  the  first,  if  measured  to  the  tip  of  its  terminal  claw. 
The  latter  is  nearly  straight,  very  slightly  recurved.  This 
joint  bears  a  single  spine  at  its  outer  distal  angle,  just  within 
which  is  the  rudiment  of  the  third  segment  of  the  ramus,  which 
bears  two  spines  similar  to  the  above,  the  inner  of  which  is  the 
longer,  the  outer  itself  being  longer  than  the  adjacent  spine 
of  the  second  joint.  Adults  of  both  sexes  are  blood-red 
throughout  except  the  egg-sac  of  the  female,  which  is  purple. 


North  American  Sjoecies  of  Diaptomus.  143 

" Dimensions  of  female:  Length  to  tip  of  caudal  setae, 
3.1  millimeters;  abdomen,  with  setae,  1.16  millimeters,  with- 
out, 0.67  millimeters;  thorax,  1.95  millimeters  in  length; 
depth,  0.725  millimeter;  width,  1  millimeter. 

"  Male  averaging  scarcely  smaller,  but  somewhat  differ- 
ently proportioned:  Thorax,  1.85  millimeters  in  length; 
depth,  0.58  millimeter;  width,  0.08  [1.08]*  millimeter; 
abdomen,  without  setae,  0.745  millimeter;  with  setae,  1.35 
millimeters  in  length. 

" Especially  abundant  in  Shoshone  Lake,  but  occurring  in 
other  lakes  and  even  in  pools  of  some  size  in  Yellowstone 
Park."! 

The  drawings  here  given  are  in  some  cases  the  same  as 
those  in  the  original  description  with  unimportant  correc- 
tions or  additions,  but  two  new  figures  (PI.  XXVI.,  Fig.  1, 
3)  have  been  added.  I  have  not  found  this  species  in  any 
collections  except  those  from  Yellowstone  Park  and  the  Flat- 
head region,  in  which  it  is  rather  abundant. 

A  few  points  may  be  added  to  the  original  description.  In 
the  female  the  first  basal  segment  of  the  fifth  pair  of  legs 
bears  a  short  sharp  spine  on  the  outer  margin  a  short  dis- 
tance above  the  distal  angle.  Both  spines  of  the  rudiment- 
ary third  segment  of  the  outer  ramus  are  distinctly  spinose 
on  the  inner  margin.  The  first  abdominal  segment  is  almost 
as  long  as  the  remainder  of  the  abdomen  ;  the  second  segment 
very  short,  about  half  as  long  as  the  succeeding  segment  or 
the  furca.  Furcal  rami  about  one  and  a  half  times  as  long 
as  wide  and  hairy  within.  My  observations  differ  from  those 
of  Prof.  Forbes  in  that,  as  a  rule,  the  abdomen  of  the  female 
is  not  asymmetrical,  the  first  segment  bearing  on  each  side  a 
small  tubercle  armed  with  a  minute  spine.  In  the  male  the 
first  abdominal  segment  is  very  slightly  dilated  laterally  but 
unarmed,  and  about  half  as  long  as  any  one  of  the  five  suc- 
ceeding segments,  which  differ  very  little  in  length.  The 
furcal  rami  are  fully  twice  as  long  as  wide  and  hairy  within. 

•The  0.08  in  the  original  description  is  probably  a  typographical  error,  since  the 
specimens  measured  by  myself  were  about  1.08  millimeters  in  length. 
tDescription  quoted  from  Forbes,  '93. 


144      Illinois  State  Laboratory  of  Natural  History. 

Diaptomus  pallidus  Herrick.    (PI.  XXVII.,  Fig.  3.) 

Diaptomus  pallidus,  Herrick,  '79,  p.  91,  PI.  II. 
Diaptomus  pallidus,  Herrick,  '83a,  p.  383,  PI.  VII.,  Fig.  1-6. 
Diaptomus  pallidus,  Herrick,  '84,  p.  142,  PI.  Q,  Fig.  17. 
Diaptomus  pallidus,  de  Guerne  et  Richard,  '89b,  p.  62,  Fig.  34. 
Diaptomus  pallidus,  Marsh,  '93,  p.  196,  PI.  III.,  Fig.  6,  7,  9. 
Diaptomus  pallidus,  Herrick  and  Turner,  '95,  p.  73,  PI.  IV,  Fig.  1-6; 
PI.  V.,  Fig.  10;  PI.  XIII.,  Fig.  17. 

Of  medium  size,  slender;  cephalothorax  widest  near  the 
middle ;  head  partially  divided  by  a  suture ;  suture  between 
head  and  thorax  distinct.  Fifth  and  sixth  thoracic  segments 
confluent ;  last  thoracic  segment  produced  laterodorsally, 
bearing  a  small  spine  on  each  side.  First  abdominal  seg- 
ment unarmed  but  dilated  laterally  (not  dilated  in  the  male), 
about  as  long  as  the  remainder  of  the  abdomen ;  second 
segment  the  shortest.    Furcal  rami  hairy  within. 

Antennae  25-segmented,  reaching  about  to  the  tips  of  the 
furca  or  slightly  beyond.  Male  prehensile  antenna  moder- 
ately swollen;  no  special  armature  on  the  last  three  seg- 
ments ;  segments  19  and  20  ankylosed,  armed  with  a  process 
and  a  long  seta;  21,  22,  and  23  ankylosed,  armed  with  two 
long  setae;  24,  with  two  long  setae;  and  25  with  four  long 
setae  and  a  sense-club.  Some  of  the  antennal  setae  are 
very  minutely  and  sparsely  hairy. 

First  basal  segment  of  right  fifth  foot  of  male  (PI.  XXVII., 
Fig.  3)  with  large  tubercle  bearing  a  small  spine  on  the  pos- 
terior aspect ;  second  basal  segment  as  usual,  about  equal  in 
length  to  the  first.  First  segment  of  the  outer  ramus  sub- 
quadrate,  about  as  long  as  wide ;  second  segment  about  as 
wide  as  the  preceding  and  about  one  and  a  half  times  as 
long,  bearing  on  the  inner  margin,  at  the  end  of  the  proxi- 
mal third,  a  small  sharp-pointed  cuticular  projection.  The 
outer  margin  of  this  segment  is  almost  straight  to  the  begin- 
ning of  the  distal  third,  where  a  sharp  angle  is  made  from 
which  springs  the  marginal  spine.  This  spine  is  sharp, 
slender,  slightly  curved,  a  little  more  than  one  third  the 
length  of  the  segment.  Terminal  hook  slender,  about  one 
and  a  half  times  as  long  as  the  second  segment ;  not  regularly 


North  American  Species  of  Diaptomus.  145 

curved,  but  with  a  sharp  angle  at  the  beginning  of  the  distal 
third  ;  minutely  denticulate  within. 

Inner  ramus  of  right  fifth  foot  one-segmented,  slender, 
narrowing  gradually  from  base  to  tip,  extending  but  slightly 
beyond  the  proximal  third  of  the  second  segment  of  the  outer 
ramus ;  hairy  at  the  apex  and  very  delicately  denticulate  on 
the  outer  margin. 

Basal  segments  of  left  fifth  foot  subquadrate,  the  second 
slightly  longer  than  the  first  and  both  slightly  longer  than 
broad;  second  segment  delicately  tuberculate  on  the  inner 
margin.  First  segment  of  outer  ramus  about  half  as  wide 
and  three  fourths  as  long  as  the  basal  segment.  Second  seg- 
ment about  as  long  as  the  first,  and  very  similar  to  the  cor- 
responding segment  of  D.  sicilis  Forbes,  from  which  it  differs, 
however,  in  its  armature.  This  consists  of  a  movable  claw,, 
blunt  or  slightly  thickened  at  the  tip,  forming  a  forcipate 
structure  with  an  inner  cushion-like  process.  The  claw 
usually  lies  close  against  this  and  is  difficult  to  make  out. 
It  is  hairy  on  both  margins. 

Inner  ramus  of  the  left  fifth  foot  one-segmented,  hairy  at 
the  apex  and  delicately  denticulate  on  the  outer  margin, 
extending  to  the  end  of  the  first  segment  of  the  outer  ramus 
or  slightly  beyond  it. 

Second  basal  segment  of  the  fifth  foot  of  the  female  with 
the  usual  hair  at  the  outer  distal  angle.  First  segment  of  the 
outer  ramus  subquadrate,  about  twice  as  long  as  broad. 
Second  segment  about  as  long  as  the  first,  tapering  to  a  blunt 
point ;  inner  margin  denticulate.  Third  segment  wanting, 
represented  by  two  spines,  the  inner  about  twice  as  long  as 
the  outer  and  smooth,  while  the  outer  is  delicately  hairy. 

Inner  ramus  of  fifth  foot  of  female  one-segmented,  reach- 
ing the  end  of  the  first  segment  of  the  outer  ramus ;  hairy  at 
the  apex  and  within,  and  armed  at  the  tip  with  two  long  sub- 
equal  delicately  hairy  spines. 

I  have  found  specimens  from  the  Illinois  River  at  Havana 
with  the  inner  ramus  of  the  right  fifth  foot  reaching  barely 
beyond  the  end  of  the  first  segment  of  the  outer  ramus.  The 
first  basal  segment  of  the  left  foot  of  the  male  is  provided  with 


146     Illinois  State  Laboratory  of  Natural  History. 

a  hyaline  lamina  ending  in  a  pointed  spine-like  projection; 
and  the  second  basal  segment  is  tuberculate  at  the  inner 
margin,  as  is  also  the  outer  margin  of  its  inner  ramus.  All 
of  these  differences  are  quite  constant  but  not  of  sufficient 
importance  to  constitute  even  a  variety. 

D.  pallidas  was  found  in  immense  numbers  in  connection 
with  D.  siciloides  Lilljeborg  during  the  entire  time  of  my  stay 
at  the  Biological  Station  at  Havana — that  is  July  and  part  of 
August,  1896.  So  far  as  I  was  able  to  ascertain,  siciloides 
was  slightly  the  more  abundant,  but  the  difference  was  not 
very  evident. 

Herrick's  original  description  of  D.  pallidus  ( '7 9)  was  very 
indefinite,  and  the  establishment  of  the  species  really  dates 
from  1893,  when  Marsh  figured  and  described  it  in  a  manner 
to  make  it  recognizable  by  later  students.  De  Guerne  and 
Eichard  ('89b)  place  it  among  their  "species  insufficiently 
described." 

Diaptomus  albuquerquensis  Herrick:.  (PI.  XXVII.,  Fig. 
2,  4.) 

Diaptomus  albuquerquensis,  Herrick,  '95,  p.  45,  Fig.  16-26. 
Diaptomus  albuquerquensis,  Herrick  and  Turner,  '95,  p.  67,  PI.  VI., 
Fig.  1-3;  PJ.  VII.,  Fig.  1-11. 

A  medium-sized  species.  Cephalothorax  widest  about  the 
middle.  Suture  between  head  and  thorax  distinct.  Last 
two  thoracic  segments,  seen  from  above,  indistinctly  conflu- 
ent, the  last  one  produced  laterodorsally  and  armed  on  each 
side  with  two  rather  long  spines ;  in  .  the  male  produced  but 
but  very  slightly  and  armed  with  only  one  spine  on  each  side. 
First  abdominal  segment  in  the  female  longer  than  the 
remainder  of  the  abdomen,  dilated  laterally,  and  armed  on 
each  side  with  a  single  spine ;  second  and  third  segments 
subequal ;  each  shorter  than  the  furcal  rami,  which  are 
barely  twice  as  long  as  wide  and  hairy  within.  .First  abdomi- 
nal segment  in  the  male  short,  a  little  more  than  half  as  long 
as  any  one  of  the  succeeding  three  segments ;  dilated  very 
slightly,  and  armed  on  each  side  with  a  spine ;  fifth  segment 
about  as  long  as  the  first.  Furcal  rami  barely  twice  as  long 
as  wide  and  hairy  within. 


North  American  Species  of  Diaptomus. 


147 


Antennae  of  the  female  2 5 -segmented,  extending  well  be- 
yond the  tips  of  the  furcal  setae ;  somewhat  shorter  in  the 
male,  reaching  about  to  the  tips  of  the  furcal  setae.  Right 
male  antenna  moderately  swollen  beyond  the  thirteenth  seg- 
ment. Beyond  the  twelfth  segment  the  antenna  is  armed  as 
follows  :  13,  with  large  process ;  14,  process,  short  seta,  and 
very  long  seta ;  15,  very  short  stunted  spine,  short  seta,  and 
long  seta;  16,  a  short  and  a  long  seta;  17,  process,  short 
seta,  and  long  seta ;  18,  large  process  ;  1 9  and  20  (completely 
ankylosed),  short  stunted  spine  and  long  seta;  20,  21,  and 
22  (also  completely  ankylosed),  two  setae,  and  a  hooked 
process  extending  beyond  the  middle  of  the  penultimate 
article;  24,  two  setae ;  and  25,  four  setae. 

Left  fifth  leg  of  the  male  (PI.  XXVII.,  Fig.  4)  short,  not 
reaching  to  the  end  of  the  second  segment  of  the  outer  ramus 
of  the  right  leg.  First  and  second  basal  segments  subequal, 
the  first  armed  at  the  middle  of  the  outer  margin  with  a 
rather  long  sharp  spine ;  the  second  slightly  broader  than 
the  first,  and  provided  a  short  distance  above  the  outer  distal 
angle  with  the  usual  delicate  hair,  and  at  the  middle  of  the 
inner  margin  with  a  small  hyaline  plate.  First  segment  of 
the  outer  ramus  about  twice  as  long  as  wide ;  outer  margin 
arcuate,  inner  margin  convex  and  delicately  hairy.  Second 
segment  racket-shaped,  the  broad  basal  half  being  almost 
circular ;  hairy  on  the  inner  margin.  The  digitiform  termi- 
nal half  is  blunt  and  delicately  denticulate  on  the  margin. 
From  the  anterior  aspect  projects  a  delicately  hairy  spine 
about  as  long  as  the  digitiform  process,  but  more  acute  and 
pointing  inward. 

Inner  ramus  of  left  fifth  leg  short,  one- segmented,  barely 
reaching  to  the  end  of  the  first  segment  of  the  outer  ramus ; 
margins  slightly  sinuous;  apex  bluntly  rounded,  very  deli- 
cately hairy,  the  hairs  at  the  apical  angles  being  somewhat 
stouter  and  spine-like. 

First  basal  segment  of  right  fifth  leg  of  male  subquadrate, 
slightly  longer  than  broad;  armed  at  the  outer  distal  angle 
with  a  stout,  sharp  spine  pointing  straight  outward.  Second 
basal  segment  subquadrate,  about  equal  to  the  first,  and 


148     Illiilois  State  Laboratory  of  Natural  History . 

armed  on  the  outer  margin,  a  short  distance  above  the  apical 
angle,  with  a  spine-like  hair.  First  segment  of  outer  ramus 
subquadrate,  slightly  narrower  than  the  second  basal  seg- 
ment, and  about  as  wide  as  long ;  second  segment  about  as 
wide  as  the  first  and  twice  as  long,  provided  at  the  end  of 
the  proximal  third  with  a  small  bead-like  tubercle.  Mar- 
ginal spine  very  large  and  strong,  longer  than  the  segment 
itself,  somewhat  sinuously  curved,  and  inserted  near  the 
distal  angle.  Terminal  hook  very  long,  as  long  as  the  remain- 
der of  the  right  leg  including  the  basal  segments,  but  not 
twice  as  long  as  the  marginal  spine ;  very  slightly  recurved 
at  the  tip  and  denticulate  at  the  inner  margin. 

Inner  ramus  of  the  right  fifth  leg  one-segmented,  very 
short,  barely  reaching  the  end  of  the  first  segment  of  the 
outer  ramus  ;  apex  bluntly  rounded  and  delicately  hairy. 

First  segment  of  outer  ramus  of  fifth  foot  of  female  (PI. 
XXVII.,  Fig.  2)  subquadrate,  about  twice  as  long  as  wide. 
Second  segment,  or  unguiform  process,  about  as  long  as  the 
first,  subcorneal  or  but  slightly  curved,  delicately  denticulate 
on  the  inner  margin.  Third  segment  small  but  distinct,  armed 
with  two  spines,  the  inner  of  which  is  more  than  twice  as 
long  as  the  outer,  reaching  about  to  the  middle  of  the  second 
segment. 

Inner  ramus  of  fifth  foot  of  female  indistinctly  two-seg- 
mented, short,  reaching  just  beyond  the  end  of  the  first  seg- 
ment of  the  outer  ramus ;  apex  bluntly  triangular,  armed 
with  a  few  short  hairs,  the  innermost  of  which  is  longer  than 
the  rest  and  spine-like. 

Length  of  female  1.2  mm. ;  of  male  1.05  mm. 

The  material  in  which  the  specimens  described  were  found 
was  loaned  me  by  Mr.  Adolph  Hempel,  of  Gotha,  Florida, 
and  was  collected  by  him  in  a  series  of  Florida  lakes  from 
January  to  March,  1896. 

D.  albuquerquensis  is  one  of  the  few  American  species  of 
Diaptomus  in  which  the  inner  ramus  of  the  fifth  leg  of  the 
female  is  two-segmented.  In  some  cases  this  ramus,  instead 
of  being  bluntly  triangular,  is  acute,  and  reaches  only  to  the 
end  of  the  first  segment  of  the  outer  ramus.    The  first  basal 


North  American  Species  of  Diaptomus.  149 

segment  is  sometimes  armed  at  the  outer  distal  angle  with 
a  short,  sharp  spine. 

Herrick  (Herrick  and  Turner,  '95)  states  that  he  found  the 
second  segment  of  the  left  fifth  leg  of  the  male  to  be  granular 
on  the  inner  margin,  and  the  marginal  spine  of  the  right  leg 
denticulate  on  the  inner  margin  and  at  the  base.  In  both 
these  respects  my  specimens  differ  from  his,  the  second  seg- 
ment of  the  left  foot  being  hairy  instead  of  granular,  and 
the  marginal  spine  of  the  right  foot  perfectly  smooth.  Her- 
rick's  statement  that  '  'the  first  pair  of  antennae  reach  to  the 
extremity  of  the  furca  or  surpass  them"  leads  me  to  think 
that  they  are  longer  in  the  Florida  .specimens  than  in  his, 
since  they  clearly  reach  beyond  the  tips  of  the  furcal  setae  in 
every  individual  which  I  have  examined. 

In  New  Mexico  Herrick  found  this  species,  in  connection 
with  D.  novamexicanus ,  in  the  water  supply  of  the  city  of 
Albuquerque;  but  in  the  Florida  lakes  it  was  found  with 
D.  mississippiensis  Marsh,  the  two  forms  being  about  equally 
abundant.  They  are  very  much  alike  in  general  appearance, 
but  the  males  may  be  distinguished  without  dissection  by  the 
antepenultimate  article  of  the  right  antenna,  which  is  armed 
in  D.  albuquerquensis  while  it  is  unarmed  in  I),  mississippien- 
sis. Herrick  gives  the  length  of  the  female  as  1.4-1.6  mm., 
but  the  largest  female  from  Florida  was  1.2  mm.,  while  the 
male  was  only  1.05  mm.  in  length,  the  average  being  con- 
siderably smaller. 

Diaptomus  novamexicanus  Herrick. 

Diaptomus  novamexicanus,  Herrick,  '95,  p.  40,  Fig.  27-29. 
Diaptomus  novamexicanus,  Herrick  and  Turner,  '95,  p.  70,  PI.  YL, 
Fig.  7-10. 

Among  the  smaller  species  of  the  genus,  moderately  robust. 
Cephalothorax  widest  somewhat  in  front  of  the  middle.  Last 
two  thoracic  segments  distinct,  the  last  armed  on  each  side 
with  a  small,  short  spine.  First  abdominal  segment  very 
long,  much  exceeding  the  remainder  of  the  abdomen,  pro- 
vided on  each  side  with  a  short,  sharp  spine;  second  seg- 
ment the  shortest.     Furcal  rami  equal  in   length  to  the 


150     Illinois  State  Laboratory  of  Natural  History. 

preceding  segment  and  about  twice  as  long  as  wide;  provided 
with  short  apical  setae. 

Antennas  of  the  female  25-segmented,  reaching  to  the  base 
or  the  end  of  the  furca.  Antepenultimate  article  of  the  right 
male  antenna  armed  with  a  lamina  produced  anteriorly  into 
an  unguiform  process  which  is  shorter  than  the  penultimate 
article. 

Outer  ramus  of  the  fifth  pair  of  feet  in  the  female  obviously 
three-segmented.  Unguiform  process  of  the  second  segment 
arcuate,  finely  denticulate  within  and  at  the  end,  armed  on 
the  outer  margin  near  the  base  of  the  last  segment  with  a 
small  spine.  Last  segment  small  but  distinct  and  armed 
with  two  short  subequal  spines. 

Inner  ramus  of  fifth  foot  of  female  one- segmented,  as  long 
as  the  basal  segment  of  the  outer  ramus ;  apex  ciliate  and 
armed  with  two  subequal  spines. 

Left  fifth  leg  of  male  reaching  slightly  beyond  the  end  of 
the  first  segment  of  the  outer  ramus  of  the  right  foot.  First 
basal  segment  armed  on  the  outer  margin  with  a  short,  sharp 
spine.  Second  segment  of  the  outer  ramus  oblong-ovate, 
armed  with  two  large  spines  ;  inner  margin  delicately  aculeate 
toward  the  apex,  and  bearing  a  ciliate  lamina. 

Inner  ramus  of  left  fifth  leg  one- segmented,  quite  long, 
reaching  beyond  the  middle  of  the  second  segment  of  the 
outer  ramus  ;  hairy  at  the  apex. 

First  basal  segment  of  right  fifth  leg  of  male  armed  on  the 
outer  margin  with  a  rather  long,  sharp  spine.  First  segment 
of  the  outer  ramus  subquadrate,  slightly  longer  than  broad ; 
second  segment  very  long  and  narrow,  more  than  twice  as 
long  as  the  preceding  segment.  Marginal  spine  slender, 
more  than  half  as  long  as  the  segment  itself,  and  inserted  at 
about  the  beginning  of  the  distal  third.  Terminal  hook  long 
and  slightly  curved. 

Inner  ramus  of  right  fifth  leg  one- segmented,  rather  long, 
reaching  beyond  the  end  of  the  first  segment  of  the  outer 
ramus  ;  apex  acute,  minutely  ciliate. 

Length  of  female  1.1-1.2  mm. 


North  American  Species  of  Diaptomus. 


151 


The  above  description  is  compiled  from  Herrick's  first 
paper  on  this  species  ('95)  and  from  the  figures  and  the 
English  and  Latin  descriptions  in  his  later  paper  (Herrick 
and  Turner,  '95).  Both  of  these  articles  are  published  as 
original  descriptions,  although  there  was  nine  months'  differ- 
ence in  the  time  of  their  appearance. 

Diaptomus  oregonensis  Lilljeborg.  (PI.  XXIX.,  Fig. 
1,  2.) 

Diaptomus  oregonensis,  de  Guerne  et  Richard,  'S9b,  p.  53,  PI.  II.,  Fig. 

5;  PI.  III.,  Fig.  8. 
Diaptomus  oregonensis,  Marsh,  '93,  p.  200,  PI.  IV.,  Fig.  4, 5. 
Diaptomus  oregonensis,  Marsh,  '95,  p.  S;  PJ.  VII.,  Fig.  5. 
Diaptomus  oregonensis,  Herrick  and  Turner,  '95.  p.  72,  PI.  IV.,  Fig. 

7-12  ;  PI.  IX.,  Fig.  3. 

A  species  of  medium  size.  Cephalothorax  widest  about 
the  middle.  The  last  two  thoracic  segments  confluent  above, 
the  last  one,  seen  from  above,  slightly  produced  laterally, 
bluntly  rounded  but  unarmed ;  in  the  male  armed  with  two 
very  minute  spines  on  each  side.  First  abdominal  segment 
as  long  as  the  rest  of  the  abdomen.*  Third  segment  and 
furcal  rami  subequal,  the  latter  about  one  and  a  half  times 
as  long  as  broad  and  delicately  hairy  within.  In  the  male 
the  first  abdominal  segment  is  short  and  unarmed ;  second 
and  third  segments  and  furcal  rami  about  equal;  fourth 
segment  the  longest,  about  equal  in  length  to  the  first  two 
segments  taken  together.   Furcal  rami  about  as  in  the  female. 

Antenna)  of  the  female  25-segmented,  extending  beyond  the 
tips  of  the  furcal  setae.  Prehensile  antenna  of  the  male  but 
slightly  swollen,  the  antepenultimate  article  entirely  unarmed. 

First  basal  segment  of  fifth  leg  of  female  (PL  XXIX.,  Fig. 
2)  with  the  usual  delicate  hair  on  the  outer  margin.  First 
segment  of  outer  ramus  about  twice  as  long  as  wide,  slightly 
arcuate,  margins  parallel ;  second  segment  about  as  long  as 
the  first,  moderately  curved,  terminating  in  an  acute  point, 

♦This  segment  had  a  very  peculiar  appearance.  Owing  to  the  thicker  anterior 
part,  the  segment  seemed  to  have  a  suture  at  about  the  middle,  and  this  was  so  mis- 
leading that  I  doubted  if  the  specimens  on  the  slideswere  really  females  until  I  could 
see  the  antenna1,  and  not  until  1  could  get  a  side  view  was  I  at  all  certain  that  there 
was  only  one  segment. 


152      Illinois  State  Laboratory  of  Natural  History. 

very  minutely  hairy  on  the  inner  margin;  third  segment 
wanting,  represented  by  two  short  spines,  the  inner  twice  as 
long  as  the  outer. 

Inner  ramus  of  fifth  leg  of  female  one-segmented,  extend- 
ing very  slightly  beyond  the  first  segment  of  the  outer  ramus  ; 
apex  obtuse,  hairy,  armed  on  the  inner  margin  and  at  the 
tip  with  two  rather  long  subequal  spines. 

First  basal  segment  of  right  fifth  leg  of  male  (PL  XXIX., 
Fig.  1)  with  a  small  tubercle  on  the  outer  margin;  second 
segment  subquadrate,  about  one  and  a  half  times  as  long  as 
the  first.  First  segment  of  the  outer  ramus  subquadrate, 
about  as  long  as  the  first  basal  segment  with  overhanging 
outer  apical  angle ;  second  segment  slightly  narrower  than 
the  first,  about  twice  as  long  as  wide,  with  a  small  projection 
at  the  middle  of  the  inner  margin.  Marginal  spine  near  the 
apical  angle,  slender,  with  a  slight  angle  about  one  fourth 
its  length  from  the  base  ;  length  about  equal  to  the  distance 
between  its  base  and  the  base  of  the  segment.  Terminal 
hook  long  and  slender,  longer  than  the  two  preceding  seg- 
ments but  not  as  long  as  those  and  the  second  basal  segment ; 
very  minutely  denticulate  on  the  inner  margin. 

Inner  ramus  of  right  fifth  leg  one-segmented,  extending  to 
a  point  about  midway  between  the  base  of  the  second  seg- 
ment of  the  outer  ramus  and  the  projection  on  the  inner 
margin  of  this  segment ;  outer  margin  hairy ;  apex  bluntly 
triangular  and  hairy. 

Second  basal  segment  of  left  fifth  leg  of  male  subquadrate, 
about  one  and  a  half  times  as  long  as  broad,  slightly  pro- 
duced on  the  inner  margin  a  short  distance  above  the  apical 
angle.  First  segment  of  outer  ramus  slightly  narrower  than 
the  second  basal  segment  and  about  twice  as  long  as  wide ; 
outer  margin  moderately  arcuate,  the  inner  margin  hairy. 
Second  segment  produced  into  three  digitiform  processes : 
the  outermost  blunt  and  by  far  the  longest ;  the  middle  one 
blunt,  barely  one  fourth  the  length  of  the  outer ;  and  the  last 
very  short,  hardly  more  than  a  tubercle,  with  an  acute  apex 
pointing  straight  inward.  The  segment  is  armed  on  the  inner 
margin  with  a  hairy,  cushion-like  process. 


North  American  Species  of  Diaptomus.  153 

Inner  ramus  of  left  fifth  leg  somewhat  spatulate,  extend- 
ing slightly  beyond  the  end  of  the  first  segment  of  the  outer 
ramus  ;  inner  margin  hairy ;  apex  bluntly  rounded  and  hairy. 

Length  of  female  1.25  mm. ;  of  male  1.15  mm. 

The  above  description  is  based  on  specimens  found  in  col- 
lections made  in  Lake  Calhoun,  Minn.,  in  July,  1891,  and 
differs  considerably  from  Lilljeborg's  original  description  in 
de  Guerne  and  Richard's  "Revision." 

He  gives  the  length  of  the  female  as  about  1.5  mm. ;  that 
of  the  male,  1.4  mm. 

I  did  not  find  in  a  single  instance  that  the  female  had  the 
last  thoracic  segment  armed  with  two  minute  spines  on  each 
side,  although  they  were  present  in  the  male.  Lilljeborg  does 
not  specify  to  which  sex  this  part  of  his  description  applied, 
but  I  assume  that  he  followed  the  usual  custom  of  referring  to 
the  female  unless  especially  stated  otherwise. 

The  spines  on  the  inner  ramus  of  the  female  I  found  to  be 
on  the  inner  instead  of  the  outer  margin,  and  they  are  so 
figured  by  Marsh  ('93). 

In  most  cases  I  found  but  one  spine  representing  the  third 
segment  of  the  outer  ramus  of  the  fifth  foot  of  the  female, 
while  one  specimen  was  found  having  one  outer  ramus  as  in 
the  type,  the  other  with  only  one  spine.  I  have  thought  it 
best  to  make  the  description  correspond  to  the  type  in  this 
particular,  regarding  the  variation  as  local  since  Marsh  ('93) 
figures  the  two  spines. 

The  inner  ramus  of  the  right  fifth  foot  of  the  male  in  the 
Minnesota  specimens  was  longer  than  represented  in  the 
original  figures,  and  hairy  on  the  inner  margin  and  at  the 
apex.  This  hairiness  is  not  mentioned  in  the  original  des- 
cription and  this  ramus  is  figured  smooth,  while  the  inner 
ramus  of  the  left  fifth  foot,  which  is  no  more  hairy  than  the 
right,  is  hairy  in  the  drawings. 

In  the  left  fifth  foot  of  the  male  the  first  segment  of  the 
outer  ramus,  although  hairy,  has  not  the  definite  cushion-like 
process  figured  by  Lilljeborg,  and  the  outer  two  digitiform 
processes  of  the  second  segment  instead  of  being  serrate 
within  are  perfectly  smooth.    From  Herrick's  statement 


154      Illinois  State  Laboratory  of  Natural  History. 

(Herrick  and  Turner,  '95,  p.  73)  that  "according  toKichard's 
drawing  the  spines  are  dentate,"  I  judge  that  he  also  found 
them  smooth,  since  his  own  figures  show  them  to  be  so. 

This  species  was  first  found  in  1888  at  Portland,  Oregon, 
by  Trybom,  and  described  in  1889  by  Lilljeborg  in  de  Guerne 
and  Kichard's  "Kevision."  Marsh  says  ('93)  that  it  is  the  most 
common  form  in  central  Wisconsin,  being  found  quite  gener- 
ally in  the  shallower  lakes,  and  that  it  occurs  in  the  Great 
Lakes,  but  not  abundantly  ('95).  Herrick  (Herrick  and 
Turner,  '95)  says  that  within  the  limits  of  Minnesota  it  had 
been  found  only  in  Lake  Minnetonka.  I  can  now  acid  Lake 
Calhoun,  Minn.,  and  Sand  Lake  in  northern  Illinois. 

Diaptomus  siciloides  Lilljeborg. 

Diaptomus  siciloides,  de  Guerne  et  Richard,  '89b,  p.  54,  PL  I.,  Fig. 
7,8,28,32.  • 

Diaptomus  siciloides,  Herrick  and  Turner,  '95,  p.  69,  PI.  VIII.,  Fig.  10. 

"Among  the  smaller  of  this  genus.  The  general  form  of  the 
body  agrees  almost  exactly  with  that  of  D.  gracilis  Sars. 
Cephalothorax  slender,  widest  at  the  middle.  The  last  two 
thoracic  segments  confluent  above.  Lateral  lobes  of  the 
last  one,  seen  from  above,  short  and  rounded,  with  rather 
large  mucros.  First  abdominal  segment  long,  fully  as  long 
as  the  remaining  part  of  the  abdomen  (without  the  setae) ; 
with  distinct  lateral  processes  at  the  anterior  part,  acuminate 
and  bending  forward  slightly.  Furcal  rami  short,  but  fully 
one  and  a  half  times  as  long  as  broad. 

"First  pair  of  antennae  of  the  female,  reflexed,  surpass  the 
furca  but  do  not  reach  the  tips  of  the  furcal  setae;  composed 
of  25  articles.  Antepenultimate  article  of  the  prehensile 
antenna  of  the  male  provided  with  a  rather  long  hook-like 
process  reaching  about  to  the  middle  of  the  penultimate 
article. 

"Fifth  pair  of  feet  in  the  female  small  but  rather  thick; 
outer  ramus  biarticulate,  hook-like  process  of  second  seg- 
ment slightly  curved,  and  almost  equal  to  the  first  segment ; 
the  inner  margin  partly  ciliate.  Inner  ramus  simple,  slightly 
longer  than  the  first  segment  of  the  outer  ramus;  with  a 
small  seta,  slightly  hairy  at  the  apex. 


North  American  Species  of  Diaptomus.  155 

"  The  inner  margin  of  the  first  segment  of  the  outer  ramus 
of  the  right  fifth  foot  of  the  male  dilated  into  a  rather  large 
hyaline  lamella.  The  second  segment  of  this  ramus  moder- 
ately curved,  the  outer  margin  obtusely  biangulate,  the  spine 
placed  below  the  middle.  Claw  simply  curved.  Inner  ramus 
small  and  slightly  surpassing  the  middle  of  the  first  segment 
of  the  outer  ramus. 

"The  second  segment  of  the  outer  ramus  of  the  left  fifth 
foot  almost  triangular,  with  a  beak-like  spine  and  delicately 
hairy  within  (intus  tenia  ore  et  subtiliter  hispido) ;  the  apical 
process  obtuse,  with  a  spine  at  the  inner  margin.  Inner 
ramus  simple,  sinuous,  and  reaching  to  or  beyond  the  middle 
of  the  second  segment  of  the  outer  ramus. 

"  Length  of  female  about  1.3  mm.;  that  of  male  slightly 
less. 

"  Found  in  the  month  of  May  in  Lake  Tulare  near  the  city 
of  Fresno,  Cal.,  by  G.  Eisen. 

"In  the  general  form  of  the  body  this  Diaptomus  closely 
resembles  D.  gracilis  Sars  as  well  as  1).  sicilis  Forbes.  It  is 
on  account  of  this  last  resemblance  that  it  was  called  siciloides. 
It  differs,  however,  from  both  :  from  D.  gracilis  in  the  shape  of 
the  last  thoracic  segment  and  of  the  abdominal  segments,  of 
the  first  pair  of  antennae,  and  of  the  fifth  pair  of  feet ;  from  D. 
sicilis  in  the  shape  of  the  fifth  pair  of  feet,  although  this  dif- 
ference is  not  very  great.  It  resembles  1).  sicilis  more  closely 
than  1).  gracilis, 

"It  seems  to  live  in  great  numbers  in  Lake  Tulare  near 
Fresno,  Cal.    The  female  bears  only  four  eggs."* 

The  statement  concerning  the  number  of  eggs  borne  by  the 
female  is  erroneous,  the  number  being  variable,  and  appar- 
ently dependent  to  a  great  degree  on  the  temperature  of  the 
water  and  on  the  food  supply.  In  the  high  mountain  lakes 
from  which  the  species  was  first  described  the  statement 
above  quoted  may  hold  true,  but  in  the  warm  sluggish  waters 
of  the  Illinois  Eiver,  where  food  is  abundant,  the  egg-sac  is 
very  large,  as  many  as  eighteen  eggs  having  been  counted 
on  a  single  female.    This  is  true  also  of  specimens  taken 


♦Lilljebortf's  description  from  tie  Guerne  et  Richard,  89b. 


156     Illinois  State  Laboratory  of  Natural  History. 

from  other  localities,  and  no  tendency  toward  constancy  in 
number  of  eggs  for  the  same  locality  was  made  out. 

The  f ureal  rami  in  both  sexes  are  hairy  within,  a  point  not 
mentioned  in  the  original  description,  although  the  rami  are 
so  figured.  All  the  specimens  which  I  examined  from  the 
various  localities  had  this  characteristic,  although  individuals 
varied  slightly  in  this  particular. 

As  mentioned  under  the  description  of  D.  pallidus,  D.  sici- 
loides  was  the  most  abundant  form  found  at  Havana.  It  also 
formed  the  greater  part  of  the  material  from  Spirit  Lake, 
Iowa,  which  was  kindly  loaned  me  by  Prof.  L.  S.  Ross,  of 
Drake  University,  Iowa. 

The  individuals  taken  from  the  Illinois  River  at  Havana, 
Illinois,  in  July  and  August,  1896,  were  all  of  an  indefinite 
color  about  like  opalescent  glass.  The  egg-sac  in  these  was 
blue,  and  there  was  a  small  pink  spot  near  the  eyes  and  just 
behind  them.  These  were  the  only  specimens  of  siciloides 
which  I  had  opportunity  to  examine  alive. 

Diaptomus  minutus  Lilljeborg.  (PI.  XXX.,  Fig.  5-8.) 

Diaptomus  minutus,  de  Guerne  et  Richard,  '89b,  p.  50,  PI.  I.,  Fig.  5, 

6, 14;  PL  III.,  Fig.  25. 
Diaptomus  minutus,  Marsh,  '93,  p.  199,  PI.  IV.,  Fig.  1-3. 
Diaptomus  minutus,  Marsh,  '95,  p.  8,  Pi.  VII.,  Fig.  3. 

' 'Among  the  smallest  of  the  genus.  Body  slender,  widest 
in  front  of  the  middle  of  the  cephalothorax  and  at  the  pos- 
terior part  of  the  head.  Fourth  and  fifth  segments  commonly 
confluent  above,  sometimes  in  the  adult  specimen  separated 
by  a  suture ;  the  lateral  lobes,  seen,  from  above,  short  and 
rounded,  and  provided  with  minute  mucros.  First  abdomi- 
nal segment  of  the  female  (PI.  XXX.,  Fig.  8)  about  as  long 
as  the  remainder  of  the  abdomen ;  rather  dilated  at  its  an- 
terior part  and  rounded  laterally ;  furnished  with  very  minute 
spines.  Second  segment  very  short,  third  segment  much 
longer,  and  these  segments  indistinctly  joined.  Furcal  rami 
about  twice  as  long  as  broad.    Furcal  setae  unusually  long. 

"First  pair  of  antennae  of  female  somewhat  surpass  the 
furca ;  composed  of  25  segments.   Antepenultimate  article  of 


North  American  Species  of  Diaptomiis.  157 


the  prehensile  antenna  of  the  male  (PL  XXX.,  Fig.  7)  with  a 
slender  process,  long  and  straight,  having  a  slight  appearance 
of  an  apical  curve,  and  extending  beyond  the  penultimate 
article  and  sometimes  almost  reaching  the  end  of  the  last 
article. 

"Setae  of  swimming  feet  unusually  long.  Outer  ramus  of 
the  fifth  pair  of  feet  in  the  female  (PL  XXX.,  Fig.  5)  bi- 
articulate ;  unguiform  process  of  second  article  slightly 
curved  and  minutely  ciliate  without.  Inner  ramus  small 
and  almost  rudimentary,  with  acuminate  apex. 

"Eight  foot  of  the  fifth  pair  of  the  male  (PL  XXX.,  Fig.  6) 
large  but  slender ;  the  second  article  of  the  outer  ramus  with 
marginal  spine  minute  and  placed  above  the  middle.  Ter- 
minal claw  thick  toward  the  base,  rather  short,  and  partly 
minutely  ciliate  within.  Inner  ramus  very  small  and  quite 
rudimentary. 

"The  left  foot  of  the  same  pair  very  similar  to  that  of  D. 
siciloides  and  D.  signicauda ;  the  second  article  of  the  outer 
ramus  almost  elliptical,  the  inner  margin  slightly  emarginate 
and  partly  ciliate  at  the  lower  part ;  with  a  large  and  obtuse 
apical  spine  and  a  smaller  inner  spine.  Inner  ramus  simple, 
attenuate  toward  the  apex,  and  extending  about  to  the  middle 
of  the  second  article  of  the  outer  ramus. 

"Length  of  female  1-1.1  mm;  of  male  hardly  1  mm. 

"Found  in  Greenland,  61°  30'- G9°  N.  Lat.,  by  Dr.  C. 
Nystrom  and  N.  0.  Hoist,  and  at  St.  John's,  Newfoundland, 
by  the  former. 

"This  species  is  distinguished  from  others  by  its  minute 
size  and  by  the  fifth  pair  of  feet.  The  female  bears  only  two 
eggs.  D.  minutus  has  been  found  in  the  Isle  of  Disko,  north- 
ern Greenland,  but  it  seems  to  be  more  common  in  the 
southern  part.  It  is  without  doubt  spread  over  the  northern 
part  of  North  America,  since  it  has  also  been  found  at  St. 
John's,  Newfoundland."* 

"We  are  able  to  confirm  in  every  respect  the  description 
given  above  by  Professor  Lilljeborg.  We  have,  in  fact,  recog- 
nized some  rare  specimens  of  7>.  minutus  in  a  collection 


*  Lilljeborg's  description  from  deGuerne  et  Richard,  89b. 


158     Illinois'  State  Laboratory  of  Natural  History. 

which  M.  Kiballier  des  Isles,  French  consul  at  Newfound- 
land, was  kind  enough  to  make  according  to  our  directions 
at  Kinney's  Pond  near  St.  John's.  This  Calanid  [centropa- 
gid]  was  found  in  great  numbers  by  M.  Ch.  Eabot  in  1888 
in  the  following  localities  in  Greenland :  Lake  Egedesminde 
(Bay  of  Disko) ;  Godhavn ;  near  the  glacier  of  Jakobshavn, 
and  in  the  Tasersuak  of  Julianehaab."* 

"Marsh  finds  this  form  in  Green  Lake  [Wisconsin],  and 
in  the  Great  Lakes;  it  may,  therefore,  be  expected  in  Lake 
Superior  in  Minnesota. "t 

Marsh  ('95)  places  sicilis  var.  imperfectus  as  a  synonym 
under  minutus,  but  does  it,  as  he  says,  "with  considerable 
hesitation."  In  looking  over  the  drawings  in  the  possession 
of  the  State  Laboratory  I  found  some  which  had  been  repro- 
duced but  not  published,  and  from  these  it  was  evident  at  a 
glance  that  the  var.  imperfectus  was  not  minutus  but  ashlandi, 
although  this  was  not  evident  from  the  description.  A  single 
specimen  of  minutus  was  found  among  the  collections  from 
Yellowstone  Park,  but  it  was  so  badly  mutilated  that  no 
drawings  could  be  made  from  it. 

Specimens  from  Greenland,  kindly  sent  me  by  Professor 
Lilljeborg,  conform  to  his  description  but  are  somewhat 
smaller  than  those  figured  by  Marsh. 

Diaptomus  trybomi  Lilljeborg.    (PI.  XXXI.,  Fig.  1-5.) 

Diaptomus  trybomi,  de  Guerne  et  Richard,  '89b,  p.  58,  PI.  I.,  Fig.  35; 

PI.  II.,  Fig.  6;  PI.  III.,  Fig.  14;  PL  IV.,  Fig.  28. 
Diaptomus  trybomi,  Herriek  and  Turner,  '95,  p.  57,  PI.  VIII.,  Fig.  17; 

PI.  IX.,  Fig.  4;  PL  X.,  Fig.  13. 

"  Of  medium  size.  Cephalothorax  widest  about  the  middle. 
Last  two  segments  distinctly  separated,  and  the  last,  seen 
from  above  (PL  XXXI.,  Fig.  3),  slightly  produced  laterally, 
provided  with  two  spines  (one  of  them  minute)  on  each 
side.  Besides  this  the  right  part  of  this  segment  (PI.  XXXI., 
Fig.  2)  bears  a  large  dorsal  appendage,  triangular  in  form, 
with  mucronate  apex,  and  extending  toward  the  right.  The 


*  de  Guerne  et  Richard,  89b. 

t  Herriek.    From  Ilerrick  and  Turner,  '95. 


North  American  Species  of  Diaptomus.  159 


first  caudal  segment  of  the  female  is  very  characteristic  of  the 
species  (in  the  male  it  is  of  the  ordinary  form)  and,  unlike 
that  of  D.  signicauda,  surpasses  in  length  the  rest  of  the 
abdomen.  This  segment  is  provided  at  the  anterior  part  on 
both  sides  with  a  short  and  mucronate  lateral  process,  and  at 
the  posterior  part  with  a  large  triangular  process  extending 
almost  directly  toward  the  right,  with  apex  slightly  acumi- 
nate.   Furcal  rami  rather  short,  not  twice  as  long  as  broad. 

"  First  pair  of  female  antennae  25 -segmented,  almost  reach- 
ing the  base  of  the  furca.  The  antepenultimate  article  of  the 
prehensile  male  antenna  (PL  XXXI.,  Fig.  1)  armed  with  an 
almost  straight  and  rather  slender  process  reaching  almost 
to  the  middle  of  the  penultimate  article,  and  provided  with- 
out with  small  teeth. 

"  Outer  ramus  of  the  fifth  pair  of  feet  in  the  female  (PL 
XXXI.,  Fig.  5)  two-segmented;  the  unguiform  process  of  the 
second  segment  slightly  curved,  robust,  moderately  ciliate 
within  and  at  the  middle  part,  last  cilium  broad,  spine-like. 
Third  segment  wanting,  produced  into  two  short  spines,  the 
outer  half  as  long  as  the  inner. 

' 'Inner  ramus  one- segmented,  almost  equal  to  the  first  seg- 
ment of  the  outer  ramus ;  apex  obliquely  acuminate,  pro- 
vided with  two  rather  long  subequal  spines. 

"  Second  segment  of  the  outer  ramus  of  the  right  fifth  foot 
of  the  male  (PL  XXXI.,  Fig.  4)  very  long,  longer  than  the 
first  segment  and  the  basal  segment  taken  together.  Margi- 
nal spine  of  this  segment  inserted  above  the  middle.  Termi- 
nal hook  slightly  curved,  inner  margin  ciliate. 

"Inner  ramus  curved,  ovate,  broad,  pointing  inward,  with 
mucronate  apex,  barely  reaching  to  the  end  of  the  first  seg- 
ment of.  the  outer  ramus. 

"  First  and  second  segments  of  the  outer  ramus  of  the 
left  foot  ciliate  within,  the  second  one  obovate,  hirsute  toward 
the  apex,  and  bearing  two  short  spines  one  of  which  points 
inward . 

"  Inner  ramus  one-segmented,  slender,  equal  to  the  first 
segment  of  the  outer  ramus." 

"Length  of  female  about  1.5  mm. ;  of  male  1.4  mm. 


160     Illinois  State  Laboratory  of  Natural  History. 

"This  species,  so  remarkable  from  the  peculiarities  pre- 
sented by  the  last  thoracic  and  the  first  abdominal  segments, 
was  found  by  the  Swedish  naturalist,  Trybom,  at  Multrooma 
Falls,  Oregon." 

The  above  is  the  description  as  given  by  Dr.  Lilljeborg 
(de  Guerne  et  Eichard,  '89b).  It  agrees  with  the  specimens 
sent  me  by  himself,  but  I  note  a  few  additional  details. 

The  abdomen  of  the  female,  seen  from  above,  is  asymmet- 
rical, as  is  also  the  last  thoracic  segment.  The  first  abdom- 
inal segment  is  dilated  anteriorly,  and  posteriorly  is  produced 
on  the  right  to  form  a  blunt,  almost  semicircular,  process. 
Seen  from  the  side  this  is  fin-shaped,  and  both  this  process 
and  the  one  on  the  last  thoracic  segment  are  penetrated  by 
muscles.    The  furcal  rami  are  hairy  within. 

In  the  male  the  peculiar  form  of  the  right  inner  ramus, 
the  extreme  shortness  of  the  left  leg,  and  the  very  irregular 
shape  of  its  last  segment  are  especially  characteristic.  The 
spines  on  the  first  basal  segment  of  each  leg  and  the  teeth 
on  the  terminal  segment  of  the  right  leg  are  also  conspicuous 
because  of  their  great  size. 

The  peculiarity  of  a  dorsal  process  is  found,  to  my  knowl- 
edge, in  but  two  other  species :  D.  sanguineus  Forbes,  and  D. 
signicauda  Lilljeborg.  In  the  small  size  of  the  inner  ramus 
of  the  right  fifth  foot  of  the  male,  D.  trybomi  approaches  the 
male  of  D.  sanguineus  Forbes,  D.  minutus  Lillj.,  and  D.  lin- 
toni  Forbes. 

De  Guerne  and  Eichard  give  Multrooma  Falls  as  the 
locality,  which  was  probably  intended  for  Multnomah  Falls, 
Oregon,  although  Prof.  Lilljeborg  in  a  personal  letter  also 
gives  the  former  spelling. 

Diaptomus  franciscanus  Lilljeborg.  (PI.  XXX., Fig.  1-4.) 

IJiaptomus  franciscanus,  de  Guerne  et  Eichard,  '89b,  p.  45,  PI.  I., 

Fig.  12,  13,  34;  PI.  III.,  Fig-.  23. 
Diaptomus  franciscanus,  Herrick  and  Turner,  '95,  p.  58,  PI.  VI1L, 

Fig.  12, 16. 

''Larger  and  more  robust  than  Diaptomus  tyrreli.  Cepha- 
lothorax  widest  in  the  middle,  and  the  last  two  segments 
confluent  above.    Lateral  lobes  of  the  last  thoracic  segment 


North  American  Species  of  Diaptomus.  161 


seen  from  above,  short  and  obtuse  posteriorly ;  armed  with 
small  spines.  First  abdominal  segment  (PI.  XXX.,  Fig.  1) 
about  equal  to  the  rest  of  the  abdomen,  moderately  dilated 
anteriorly,  rounded  at  the  sides,  and  armed  here  with  small 
spines  or  mucros ;  always  destitute  of  all  lateral  processes. 
An  imperfect  suture  remains  long  after  maturity  in  the  pos- 
terior part  of  this  segment.  Second  segment  of  the  abdomen 
much  shorter  than  the  third,  and  also  more  slender  and 
easily  pushed  within  the  preceding  joint.*  Furcal  rami  short, 
fully  one  and  a  half  times  longer  than  broad ;  sparsely  ciliate 
within. 

"First  pair  of  antennae  of  female,  reflexed,  extend  about 
to  the  furca ;  composed  of  25  articles.  Antepenultimate 
article  of  the  male  prehensile  antenna  (PI.  XXX.,  Fig.  2) 
provided  with  an  unguiform  process,  slightly  surpassing  the 
end  of  the  penultimate  article. 

"Outer  ramus  of  the  fifth  pair  of  feet  in  the  female  (PI. 
XXX.,  Fig.  4)  three-segmented,  the  third  segment  very  small 
but  distinct,  and  bearing  two  spines.  The  unguiform  process 
of  the  second  segment  of  this  ramus  rather  arcuate  and  finely 
ciliate  within  at  the  lower  part,  the  last  spine  thicker  than 
the  rest.  Inner  ramus  simple  and  equal  to  the  first  segment 
of  the  outer  ramus,  bearing  two  long  equal  spines  at  the 
apex,  of  which  the  outer  is  ciliate  within  at  the  base. 

"The  right  fifth  foot  of  the  male  (PI.  XXX.,  Fig.  3)  rather 
robust.  The  second  segment  of  the  outer  ramus  almost  rect- 
angular and  comparatively  short ;  the  outer  marginal  spine 
placed  near  the  apex,  and  the  inner  margin  armed  with  a  mi- 
nute spine.  Terminal  hook  long,  distinctly  sigmoid  or  S- 
shaped  and  tapering  toward  the  apex.  Inner  ramus  small 
and  barely  reaching  the  middle  of  the  second  article  of  the 
outer  ramus ;  either  imperfectly  two-segmented  or  one- 
segmented  and  armed  with  an  apical  spine. 

"The  second  segment  of  the  outer  ramus  of  the  left  fifth 
foot  of  the  male  lamelliform,  almost  triangular,  and  thinner 
within.   This  segment  on  the  thicker,  outer,  side  bears  a  short 

♦The  meaning  of  the  original  at  this  point  is  rather  obscure.  It  reads:  "Sea- 
mentum  2-dum  caudce  3-tio  multo  brevius  ejusque  testa  tenuior  et  facile  adstrin- 
aenda." 


162     Illinois  State  Laboratory  of  Natural  History. 


spine  in  the  middle,  and  ends  in  a  short  obtuse  process,  the 
inner  apical  angle  of  which  exhibits  three  small  oblique  in- 
cisions. The  inner  margin  is  minutely  ciliate.  The  inner 
ramus  is  simple  and  slender,  attenuate  toward  the  apex,  and 
reaching  about  to  the  middle  of  the  second  segment  of  the 
outer  ramus. 

"Length  of  female,  2.3  mm. ;  of  male,  2.0  mm. 

"Found  near  San  Francisco  by  G.  Eisen. 

"This  Diaptomus  approaches  D.  longicornis  var.  similis 
Herrick  in  the  shape  of  the  body  and  of  the  lateral  lobes  of 
the  last  thoracic  segment,  but  it  differs  greatly  in  respect  to 
the  fifth  pair  of  feet,  especially  in  the  male.  It  seems  to  be 
common  in  the  vicinity  of  San  Francisco,  hence  the  name, 
franciscanus."* 

The  female  is  conspicuous  chiefly  for  the  extremely  long 
spines  with  which  the  inner  rami  of  the  fifth  pair  of  feet  are 
armed.  These  are  about  as  long  as  the  ramus  itself  and 
hairy  at  the  base.  The  thorax  and  abdomen  are  of  ordinary 
form.  The  furca  are  hairy  within,  and  also,  but  more 
sparsely,  on  the  outer  margin.  In  the  male  the  outer  margin 
is  not  hairy. 

The  outer  ramus  of  the  left  fifth  foot  of  the  male  is  termi- 
nated by  a  peculiarly  flattened  segment  (PL  XXX.,  Fig.  3). 
In  a  male  of  this  species  sent  me  by  Professor  Lilljeborg, 
both  inner  rami  of  the  fifth  pair  of  legs  are  two- segmented. 

Diaptomus  eiseni  Lilljeborg. 

Diaptomus  eiseni,  de  Guerne  et  Kichard,  '89b,  p.  44,  PI.  I.,  Fig.  19, 
29,  33.f 

Diaptomus  eiseni,  Herrick  and  Turner,  '95,  p.  58,  PI.  X.,  Fig.  11. 

"Among  the  largest  of  the  genus.  Cephalothorax  widest  at 
the  posterior  part  of  the  head.  The  last  two  thoracic  seg- 
ments usually  confluent  above  or  indistinctly  segmented,  and 
the  lateral  lobes  of  the  last  segment,  seen  from  above,  short 

*Lilljeborg's  description  and  remarks  from  de  Guerne  et  Richard,  '89b. 

t  Confusion  maybe  caused  by  a  slight  mistake  which  crept  into  de  Guerne  and 
Richard's  "Revision."  In  the  index  and  under  the  species  names,  Fig.  20,  PI.  I.  is 
given  as  the  fifth  foot  of  D-  serricornis  and  also  of  D.  eiseni.  The  "explanation  of 
plates1  however,  gives  Fig.  29,  PI.  I.,  as  that  of  D.  eiseni,  which  by  comparison  with 
the  description  is  found  to  be  correct. 


Nortli  American  Species  of  Diaptomus.  163 


in  the  female;  upper  posterior  angle  rather  acute,  lateral 
angle  very  obtuse,  the  spines  of  both  angles  thick  and  short. 
First  abdominal  segment  slightly  longer  than  the  remainder  of 
the  abdomen  (seta?  excepted),  produced  anteriorly  into  a  rather 
large  lateral  process  with  spines  pointing  obliquely  backward. 
Second  abdominal  segment  very  short.  Furcal  rami  short ; 
sparsely  hairy ;  about  one  and  a  half  times  as  long  as  broad. 

"First  pair  of  antennae  reach  to  the  lateral  processes  of  the 
first  abdominal  segment;  composed  of  25  segments.  Ante- 
penultimate article  of  the  prehensile  antenna  of  the  male 
with  a  long  curved  and  acuminate  process  almost  surpassing 
the  end  of  the  antenna. 

"Outer  ramus  of  the  first  pair  of  feet,  especially  in  the 
female,  pectinately  setose. 

"Outer  ramus  of  the  fifth  pair  of  feet  in  the  female  two- 
segmented,  the  second  segment  with  large  unguiform  process 
within  and  heavily  spined  without.  The  inner  ramus  of  this 
foot  rather  long,  clearly  not  reaching  the  end  of  the  first  seg- 
ment of  the  outer  ramus;  suture  sharply  indicated;  pro- 
vided at  the  apex  with  two  spine-like  setae  and  within  with 
minute  spines. 

"Eight  fifth  foot  of  the  male  rather  robust.  Second  basal 
segment  dilated  within  into  a  rugose  lamella  ;  second  segment 
of  the  outer  ramus  with  marginal  spine  placed  near  the  apex. 
Inner  margin  of  terminal  claw  slightly  sigmoid ;  from  the 
middle  toward  the  apex  first  delicately  pectinately  spined, 
and  thence  tuberculate.  Inner  ramus  small  and  indistinctly 
two-segmented,  extending  slightly  beyond  the  middle  of  the 
second  segment  of  the  outer  ramus ;  armed  at  the  apex  with 
a  spine,  and  at  the  same  place  and  within  with  thick  cilia. 

"Left  foot  of  the  fifth  pair  of  the  male  much  smaller  than 
the  right.  Second  or  last  segment  of  the  outer  ramus  of  this 
foot  with  the  apex  narrowed  but  obtuse,  and  within  this  an 
acuminate  spine ;  an  emarginate  narrow  and  hairy  lamina 
on  the  inner  margin.  Inner  ramus  slender,  rather  long,  and 
notably  surpassing  the  middle  of  the  second  segment  of  the 
outer  ramus ;  indistinctly  two-segmented,  the  apex  similar 
to  that  of  the  right  inner  ramus. 


164     Illinois  State  Laboratory  of  Natural  History. 


"Length  of  female,  4  mm. ;  of  male,  3.5  mm. 

"Found,  near  Fresno,  Cal.,  by  G.  Eisen,  the  Swedish  zoolo- 
gist, member  of  the  San  Francisco  Scientific  Academy." 

"This  Diaptomus  is  dedicated  to  Mr.  G.  Eisen,  who  found 
it  in  California  with  a  great  number  of  other  Entomostraca. 
It  was  given  by  him  to  the  Zoological  Museum  of  the  Uni- 
versity of  Upsala.  D.  eiseni  is  very  distinct  from  all  the 
American  species  described  by  Profs.  Forbes  and  Herrick."* 

The  last  thoracic  segment  of  the  female  is  strongly  pro- 
duced posteriorly  and  the  first  abdominal  segment  is  moder- 
ately dilated  and  armed  on  each  side  with  a  large  spine. 
This  form  may  also  be  recognized  on  account  of  its  great 
size,  being  but  little  smaller  than  D.  stagnalis  or  D.  shoshone 
Forbes.  The  fifth  pair  of  legs  are  remarkable  for  the  ex- 
treme size  of  the  inner  of  the  two  spines  representing 
the  third  segment  of  the  outer  ramus,  which  is  made  still 
more  striking  by  a  row  of  strong  teeth  on  each  margin.  The 
second  segment  of  the  outer  ramus  is  also  armed  with  strong 
teeth  on  the  inner  margin. 

The  fifth  pair  of  legs  of  the  male  may  be  easily  recognized 
from  the  fact  that  at  least  an  indication  of  a  suture  is  found 
on  each  inner  ramus,  making  it  indistinctly  two-segmented. 
The  rugose  lamella  on  the  second  basal  segment  of  the  right 
fifth  leg  is  also  very  characteristic. 

Diaptomus  signicaudaLiLLjEBORG.  (PI.  XXIX.,  Fig.  3-6.) 

Diaptomus  signicauda,  de  Guerne  et  Richard, '89b,  p.  55,  PI.  I.,  Fig. 

15,16,31;  PI.  III.,  Fig.  22. 
Diaptomus  signicaudatus ,  Herrick  and  Turner,  '95,  p.  63,  PI.  VIII., 

Fig.  13 ;  PI.  IX.,  Fig.  10. 

"This  species  is  among  the  smaller  species  of  this  genus. 
Form  Of  the  body  very  slender.  Cephalothorax  widest  in  front 
of  the  middle,  at  the  second  segment.  Last  two  segments  of 
the  thorax  (PI.  XXIX.,  Fig.  6)  confluent  above,  the  last,^  seen 
from  above,  with  rather  large  and  projecting  lateral  lobes, 
posterior  angles  acute,  with  small  spines.  Fourth  thoracic 
segment,  seen  from  the  side,  provided  above  with  a  small 

*Lilljeborg's  description  and  remarks  from  de  Guerne  et  Richard,  '89b. 


North  American  Species  of  Diaptomus. 


165 


hump.  First  abdominal  segment  of  the  female  very  char- 
acteristic of  the  species,  giving  to  it  its  name.  This  seg- 
ment is  provided  at  the  anterior  part  with  short,  mucronate 
lateral  processes,  and  at  the  posterior  part  on  the  right  side 
with  a  large  process  bent  obliquely  backward  and  moderately 
acuminate.  Besides  this  an  indication  of  a  suture  is  also 
often  present.  The  length  of  this  segment,  posterior  process 
excepted,  is  slightly  less  than  the  remainder  of  the  abdomen. 
Furcal  rami  hardly  more  than  half  as  long  as  broad. 

"First  pair  of  antennae  of  the  female  always  25-segmented ; 
reflexed,  slightly  surpass  the  furcal  rami,  but  do  not  reach 
the  end  of  the  furcal  setae.  The  antepenultimate  article  of 
the  prehensile  antenna  of  the  male  (PI.  XXIX.,  Fig.  4)  armed 
with  a  medium-sized  hook-like  process. 

"  Fifth  pair  of  feet  of  female  (PI.  XXIX.,  Fig.  5)  very  simi- 
lar to  the  corresponding  pair  of  D.  siciloides.  Outer  ramus 
two-segmented;  unguiform  process  of  the  second  segment 
slightly  curved,  almost  parallel  with  the  first  article ;  very  deli- 
cately ciliate  within,  the  last  cilia  thicker  and  spine-like. 

"Inner  ramus  one-segmented,  longer  than  the  first  seg- 
ment of  the  outer  ramus ;  apex  obliquely  acuminate  and 
ciliate,  and  bearing  two  equal  ciliate  spines. 

"The  right  fifth  foot  of  the  male  (PI.  XXIX.,  Fig.  3)  rather 
slender.  First  segment  of  the  outer  ramus  dilated  within 
into  a  small  hyaline  lamina.  The  second  segment  as  long  as 
the  first  article  and  the  second  basal  segment  together.  The 
marginal  spine  of  the  second  segment  is  situated  a  little 
below  the  middle.    Terminal  hook  simply  curved. 

"Inner  ramus  rather  broad,  acuminate,  and  short,  not 
reaching  to  the  end  of  the  first  segment  of  the  outer  ramus. 

'  The  second  segment  of  the  outer  ramus  of  the  left  foot 
elliptical  or  oblong-ovate ;  within  and  toward  the  apex  very 
delicately  aculeate,  and  bearing  two  large  spines,  one  of 
which  inclines  inward. 

"  Inner  ramus  simple  and  slender,  but  long,  and  extending 
beyond  the  middle  of  the  second  segment  of  the  outer  ramus. 

"Length  of  female  about  1.5  mm. ;  of  male,  1.3  mm. 


166      Illinois  State  Laboratory  of  Natural  History. 

"Found  in  the  Sierra  Nevada  Mountains,  California,  at  a 
height  of  from  8,000-10,000  feet  above  sea-level  by  G. 
Eisen.  Appears  to  be  very  common  in  small  pools  in  this 
locality. 

"This  Diaptomus  is  very  distinct  from. all  known  species 
on  account  of  the  peculiar  form  of  the  first  abdominal  seg- 
ment. In  this  respect  it  approaches  D.  roubaui  Eichard,  and 
the  genus  Epischura  Forbes.  In  the  case  of  these  Copepoda, 
however,  it  is  the  male  which  is  distinguished  by  the  irregu- 
larity of  the  abdomen.  The  name  which  I  have  given  it 
refers  particularly  to  the  shape  of  the  female  abdomen."* 

There  is  nothing  to  acid  to  the  above  description  of  this 
species  except  that  the  furca  are  delicately  hairy  within,  a  fact 
neither  shown  in  the  drawings  nor  mentioned  in  the  original 
description.  The  last  thoracic  segment  of  the  female  is 
strongly  produced,  and  the  first  abdominal  segment  greatly 
dilated  at  its  anterior  part.  The  process  on  the  first  abdomi- 
nal segment  is  even  larger  in  some  cases  than  represented  in 
the  original  drawings. 

In  the  male  also  the  last  thoracic  segment  is  produced,  but 
not  so  much  as  in  the  other  sex.  The  fifth  pair  of  legs  are 
very  similar  to  those  of  D.  siciloides,  from  which  they  may  be 
distinguished  by  the  shape  of  the  right  inner  ramus  and  of 
the  hyaline  lamina  on  the  first  segment  of  the  outer  ramus  of 
the  right  fifth  leg.  Both  inner  rami  are  delicately  hairy,  but 
I  fail  to  find  the  smooth,  cushion-like  process  on  the  outer 
margin  and  at  the  base  of  the  left  inner  ramus  which  is  fig- 
ured in  the  original  drawings  but  of  which  no  mention  is 
made  in  the  text. 

The  females  of  D.  signicauda  and  D.  trybomi  both  have  a 
"dorsal  process,"  and  in  this  respect  approach  D.  sanguineus 
Forbes. 

Individuals  of  this  species  were  kindly  sent  me  by  Dr. 
Lilljeborg,  but  were  unavoidably  delayed  until  after  this 
description  was  completed.  There  was  no  time  to  rewrite  it, 
hence  these  remarks  are  in  the  form  of  addenda.  The  same 
is  true  of  trybomi,  eiseni,  and  franciscanus. 

*Lilljeborg's  description  and  remarks  from  de  Guerne  et  Richard,  '89b. 


North  American  Species  of  Diaptomus,  167 


Diaptomus  ashlandi  Marsh.    (PL  XXXII.,  Fig.  1-4.) 

Diaptomus  sicilis  var.  imperfectus,  Forbes  '90,  p.  703. 
Diaptomus  ashlandi,  Marsh,  '93,  p.  198,  PI.  III.,  Fig.  11-13. 
Diaptomus  ashlandi,  Herrick  and  Turner,  '95,  p.  60,  PI.  VI.,  Fig.  4-6. 
Diaptomus  ashlandi,  Marsh,  '95,  p.  7,  PI.  VII.,  Fig.  2. 

A  small,  slender  species,  about  the  same  width  throughout. 
Suture  between  head  and  thorax  distinct.  Last  two  thoracic 
segments  distinct,  the  last  one  strongly  bifid  and  armed  on 
each  side  with  a  small  blunt  spine.  Abdomen  long  and 
narrow ;  inclusive  of  the  furca,  about  half  as  long  as  the  ceph- 
alothorax.  First  abdominal  segment  as  long  as  the  remainder 
of  the  abdomen  exclusive  of  the  furcal  rami ;  dilated  laterally ; 
with  a  small  spine  on  each  side  (unarmed  in  the  male).  Second 
and  third  segments  subequal.  Furcal  rami  barely  twice  as 
long  as  wide ;  hairy  within. 

Antennae  25-segmented,  reaching  to  the  base  of  the  furcal 
rami  or  slightly  beyond.  Prehensile  antenna  (PI.  XXXII., 
Fig.  4)  moderately  swollen;  segments  19,  20,  and  21,  and 
22  and  23,  ankylosed ;  process  on  the  antepenultimate  seg- 
ment extending  almost  to  the  middle  of  the  last  segment,  the 
end  knobbed  and  roughened  or  tuberculate  at  the  inner 
margin. 

Fifth  pair  of  legs  of  the  male  (PL  XXXII.,  Fig.  3)  rather 
slender ;  left  leg  reaching  about  to  the  end  of  the  first  seg- 
ment of  the  outer  ramus  of  the  right  leg.  On  the  anterior 
surface  of  the  first  basal  segment  of  the  right  leg  is  a  large 
tubercle  bearing  at  the  tip  a  small  acute  spine.  Second 
basal  segment  without  special  characteristics.  First  seg- 
ment of  the  outer  ramus  subquadrate,  slightly  broader  than 
long;  inner  apical  angle  somewhat  produced,  the  process 
ending  in  an  acute  point.  Second  segment  about  three  times 
as  long  as  the  first,  with  a  sharp  angle  at  end  of  proximal 
third,  from  the  point  of  which  springs  the  lateral  spine.  This 
is  about  half  as  long  as  the  segment,  with  an  angle  near  its 
base.  Terminal  hook  long  and  slender,  rather  more  robust 
than  that  of  />.  sicilis  Forbes,  but  shaped  very  much  like  it; 
minutely  denticulate  on  the  inner  margin. 


168      Illinois  State  Laboratory  of  Natural  History. 

Inner  ramus  of  right  fifth  leg  one- segmented,  very  narrow, 
extending  about  half  its  length  beyond  the  end  of  the  first 
segment  of  the  outer  ramus ;  apex  with  an  acute  triangle, 
hairy  at  the  tip  ;  sides  parallel. 

First  basal  segment  of  the  left  fifth  leg  produced  on  the 
anterior  aspect,  near  the  outer  margin,  into  a  long  tubercle 
ending  in  a  minute,  sharp  spine ;  second  basal  segment  with 
delicate  hair  near  the  outer  distal  angle.  First  segment  of 
the  outer  ramus  subquadrate,  shorter  than  the  preceding, 
slightly  longer  than  broad ;  second  segment  about  as  long  as 
the  first  and  about  twice  as  long  as  wide ;  very  similar  to  the 
corresponding  segment  of  D.  sicilis  Forbes. 

Inner  ramus  of  left  fifth  leg  long  and  narrow,  margins  sin- 
uously curved;  extending  about  to  the  middle  of  the  last 
segment  of  the  outer  ramus ;  delicately  hairy  at  the  tip. 

Second  basal  segment  of  fifth  leg  of  female  (PI.  XXXII., 
Fig.  1,  2)  with  the  usual  delicate  hair  at  the  outer  margin. 
First  segment  of  the  outer  ramus  about  twice  as  long  as 
wide  ;  second  segment  somewhat  longer  than  the  first,  taper- 
ing to  a  rather  sharp  point  and  curving  outward  slightly, 
delicately  denticulate  on  the  inner  margin;  third  segment 
wanting,  represented  by  two  spines,  the  outer  about  twice  as 
long  as  the  inner. 

Inner  ramus  one-segmented,  extending  slightly  beyond 
first  segment  of  the  outer  ramus,  hairy,  ending  in  acute  tri- 
angular tip ;  armed  at  the  apex  with  two  rather  long  sub- 
equal  spines  which  are  sometimes  hairy. 

Length  of  female  .97  mm. ;  of  male  .9  mm. 

A  reference  to  the  "  Distribution  of  American  Species"  (see 
page  183),  will  show  the  wide  range  of  this  form.  In  the 
collections  of  the  U.  S.  Fish  Commission  from  Lake  Samma- 
mish,  Lake  Union,  and  Lake  Washington,  Wash. ;  Tsiltcoos 
Lake,  Tahkenitch  Lake,  and  Klamath  Lake,  Oregon ;  and 
Lake  Pend  d'  Oreille  and  Gamble's  Lake,  Idaho,  D.  ashlandi 
was  found  in  immense  numbers,  being  either  the  only  centro- 
pagid  or  occurring  in  connection  with  Epischura  nevadensis 
Lilljeborg. 


North  American  Species  of  Diaptomus.  169 


Diaptomus  ashlandi  is  very  similar  to  D.  sicilis  Forbes  and 
hardly  to  be  distinguished  from  it  but  for  a  slight  difference  ^ 
in  the  last  segment  of  the  left  fifth  foot  of  the  male  and  the 
position  of  the  marginal  spine  of  the  right  fifth  foot.  In  the 
Laboratory  collections  from  Yellowstone  Park  and  the  Flat- 
head region  of  Montana  forms  occur  which  seem  to  be  inter- 
mediate between  the  two,  and  it  was  exceedingly  difficult  to 
decide  to  which,  if  either,  of  the  two  species  they  belonged. 
D.  ashlandi  seems  to  me,  however,  to  be  a  good  species,  since 
the  form,  as  described  by  Marsh  ('93  and  '95)  and  as  found 
by  myself  in  other  collections,  exhibits  constant,  though  some- 
what minute,  differences  from  sicilis  hard  to  describe,  but  at 
once  evident  from  the  figures. 

A  very  peculiar  modification  of  the  inner  ramus  of  the  fifth 
foot  of  the  female  was  noted  in  a  specimen  taken  from  an 
alkaline  pond  in  Yellowstone  Park.  In  this  individual  one  of 
the  feet  (PI.  XXXII.,  Fig.  1)  was  normal  in  every  respect, 
while  the  inner  ramus  of  the  other  was  armed  on  its  outer 
margin,  at  the  end  of  the  proximal  third,  with  a  sharp,  smooth 
spine  about  half  as  long  as  the  ramus  itself. 

D.  sicilis  var.  imperfectus  Forbes  ('90)  is  here  made  a  syn- 
onym of  D.  ashlandi,  because  unpublished  Laboratory  draw- 
ings of  that  variety  clearly  show  it  to  be  such.  Marsh's  de- 
scription must  stand,  since  the  description  of  imperfectus  was 
not  complete  enough  to  identify  the  form.  This  species  was 
also  noticed  by  Dr.  Forbes  in  the  collections  reported  on  in 
'93,  but  was  erroneously  regarded  by  him  as  an  immature 
form  of  D.  sicilis. 

Diaptomus  reighardi  Marsh.    (PI.  XXVIII.,  Fig.  1.) 

Diaptomus  reighardi,  Marsh,  '95,  p.  9,  PI.  I.,  Fig.  1-4. 

A  medium-sized  species ;  body  about  the  same  width 
throughout.  Sutures  between  the  first  and  second,  and  between 
the  last  two,  thoracic  segments  distinct ;  last  thoracic  seg- 
ment not  produced,  armed  on  each  side  with  a  very  minute 
spine.  First  abdominal  segment  almost  as  long  as  the  rest 
of  the  abdomen,  dilated  laterally,  armed  on  each  side  with  a 


170      Illinois  State  Laboratory  of  Natural  History. 

minute  spine ;  second  and  third  segments  subequal ;  furcal 
rami  slightly  longer  than  the  third  segment,  about  twice  as 
long  as  wide ;  and  delicately  hairy  within.  In  the  male  the 
second  abdominal  segment  and  the  furcal  rami  are  subequal, 
and  each  is  longer  than  any  of  the  other  segments.  The 
furcal  rami  are  considerably  longer  than  the  preceding  seg- 
ment, fully  twice  as  long  as  wide,  and  hairy  within. 

Antennse  "2  5 -segmented,  reaching  well  beyond  the  tips  of 
the  furcal  setae.  Eight  male  antenna  not  much  swollen 
anterior  to  the  geniculate  joint*  antepenultimate  segment 
unarmed. 

Left  fifth  leg  of  male  (PI.  XXVIII.,  Fig.  1)  short,  extending 
beyond  the  middle,  but  not  reaching  the  end  of  the  second 
segment,  of  the  outer  ramus  of  the  right  leg.  First  basal 
segment  armed  at  the  outer  distal  angle  with  a  short,  sharp 
spine.  Second  basal  segment  about  equal  to  the  first,  almost 
as  wide  as  long.  First  segment  of  the  outer  ramus  irregularly 
trapezoidal  in  form,  about  half  as  wide  as  the  second  basal 
segment,  and  delicately  hairy  on  the  inner  margin.  Second 
segment  somewhat  as  in  D.  oregonensis  Lilljeborg.  It  is  pro- 
duced into  two  digitiform  processes,  the  outer  of  which  is 
more  than  twice  as  long  as  the  inner  and  armed  on  the  inner 
margin  at  the  tip,  with  a  small  cushion-like.,  delicately  hairy 
process.  There  is  a  distinct  suture  between  the  main  part  of 
the  second  segment  and  the  inner  of  the  two  processes,  and  the 
process  itself  is  minutely  denticulate  on  the  outer  margin. 

Inner  ramus  of  left  fifth  leg  one-segmented,  reaching  to  the 
base  of  the  inner  digitiform  process ;  outer  margin  hairy, 
almost  straight ;  inner  margin  somewhat  sinuously  curved. 

First  basal  segment  of  the  right  fifth  foot  of  the  male  sub- 
quadrate,  slightly  longer  than  wide,  armed  at  the  outer  distal 
angle  with  a  short,  sharp  spine.  Second  segment  about  as 
wide  as  the  first  and  one  and  a  half  times  as  long ;  provided 
with  the  usual  hair  on  the  outer  margin.  First  segment  of  the 
outer  ramus  a  little  more  than  half  as  long  as  the  second 
basal  segment  and  slightly  longer  than  wide  ;  second  segment 
less  than  half  as  wide  as  long  and  more  than  twice  as  long  as 
the  preceding  segment.    Marginal  spine  rather  short,  about 


North  American  Species  of  Diaptomus.  171 

as  long  as  the  segment  is  wide ;  inserted  near  the  beginning 
of  the  distal  third ;  slightly  curved  and  distinctly  denticulate 
on  the  inner  margin.  Terminal  hook  rather  slender,  a  little 
more  than  twice  as  long  as  the  preceding  segment ;  not  regu- 
larly curved,  but  divided  approximately  into  thirds  by  abrupt 
angles,  the  upper  one  very  sharp,  below  which  on  the  inner 
margin,  the  hook  is  delicately  but  distinctly  denticulate. 

Inner  ramus  of  right  fifth  foot  short,  one-segmented,  reach- 
ing just  to,  or  extending  very  slightly  beyond,  the  end  of  the 
first  segment  of  the  outer  ramus  ;  apex  bluntly  triangular  and 
delicately  hairy. 

First  segment  of  the  outer  ramus  of  the  fifth  leg  of  the 
female  subquadrate,  about  twice  as  long  as  wide  :  second  seg- 
ment slightly  shorter  than  the  first,  moderately  curved,  the 
inner  margin  distinctly  denticulate ;  third  segment  wanting, 
being  represented  by  two  spines ;  the  outer  short  and  thick 
and  only  about  half  as  long  as  the  inner. 

Inner  ramus  of  fifth  leg  of  female,  one-segmented,  extending 
slightly  beyond  the  end  of  the  first  segment  of  the  outer  ramus  ; 
delicately  hairy  at  the  apex  and  on  the  distal  fourth,  and 
armed  in  addition  to  this  with  two  slender  spines  about  as  long 
as  the  shorter  of  the  two  representing  the  third  segment  of 
the  outer  ramus. 

Length  of  female,  1.1395  mm. ;  of  male,  1.0248  mm. 

The  above  measurements  are  those  of  Professor  Marsh. 
The  largest  female  I  examined  was  1.13  mm.  in  length,  the 
smallest,  1  mm.;  while  the  largest  male  I  measured  was  1 
mm.  in  length,  the  smallest,  .96  mm. 

Prof.  Marsh  originally  described  this  species,  and  I  am 
greatly  indebted  to  him  for  the  specimens  from  which  the 
above  description  was  made.  He  found  D.  reighardi  in  only 
three  localities,  all  in  Michigan  ;  North  Lake,  on  Beaver 
Island,  Intermediate  Lake,  and  Crooked  Lake.  I  do  not 
know  of  its  having  been  recorded  from  any  other  place. 

At  first  sight  D.  reigha/rdi,  in  respect  to  the  fifth  pair  of 
legs  of  the  male,  is  very  like  D.  oregonensis  Lilljeborg,  but 
the  details  of  structure  are  very  different  in  the  two,  and  there 
can  be  no  doubt  as  to  the  validity  of  the  species. 


172     Illinois 'State  Laboratory  of  Natural  History. 

Diaptomus  birgei  Marsh. 

Diaptomus  birgei,  Marsh, '94,  p.  16,  PI.  I.,  Fig.  4-6. 
Diaptomus  birgei,  Herri ck  and  Turner,  '95,  p.  79,  PI.  XL VII.,  Fig. 
4-6. 

"  Of  moderate  size.  The  first  segment  of  the  cephalothorax 
is  nearly  equal  in  length  to  the  three  following.  The  first 
segment  of  the  abdomen  of  the  female  is  as  long  as  the 
remainder  of  the  abdomen  and  the  furca.  It  is  much  dilated 
in  front.  The  second  segment  is  nearly  twice  as  long  as  the 
third,  and  about  equal  in  length  to  the  furca.  The  second 
and  third  joints  are  very  closely  united. 

"The  antennae  extend  to  the  end  of  the  furca.  The  right 
antenna  of  the  male  is  much  swollen  anterior  to  the  geniculat- 
ing  joint;  the  antepenultimate  joint  is  produced  on  its  distal 
end  into  a  short,  blunt  process,  which  makes  very  nearly  a 
right  angle  with  the  longitudinal  axis  of  the  joint. 

"  The  outer  ramus  of  the  fifth  foot  of  the  female  is  two- 
jointed,  the  third  joint  being  represented  by  two  spines.  The 
inner  ramus  is  one- jointed,  hardly  as  long  as  the  first  joint 
of  the  outer  ramus,  and  armed  at  the  tip  with  minute  setae 
and  two  rather  long  spines. 

"  The  basal  joint  of  the  right  fifth  foot  of  the  male  is  elon- 
gated, trapezoidal  in  form,  its  greatest  breadth  being  at  its 
distal  extremity.  The  first  joint  of  the  outer  ramus  is  broader 
than  long,  armed  on  its  inner  margin  with  a  broad,  thin  ex- 
pansion of  the  integument.  The  second  joint  is  elongate, 
broader  at  base;  the  lateral  spine  is  situated  at  about  the 
middle  of  its  length,  is  long  and  stout,  and  armed  on  its  inner 
margin  with  fine  serrulations.  The  terminal  hook  is  slightly 
angular,  and  armed  with  fine  serrulations  on  its  inner  mar- 
gin. The  inner  ramus  is  one-jointed,  equaling  in  length  the 
first  joint  of  the  outer  ramus. 

"  The  left  fifth  foot  of  the  male  reaches  slightly  beyond  the 
first  joint  of  the  outer  ramus  of  the  right.  The  basal  joint  is 
quadrangular,  considerably  shorter  than  the  right  basal  joint. 
The  first  joint  of  the  outer  ramus  is  about  twice  as  long  as 
broad.  The  second  joint  is  slightly  longer  than  the  first  joint ; 
it  is  expanded  at  base,  where  it  is  armed  with  fine  hairs,  and 


North  American  Species  of  Diaptomus.  173 


terminates  in  a  finger-like  process  bearing  a  falciform  spine. 
The  inner  ramus  extends  to  about  one  half  the  length  of  the 
second  joint. 

"Length  of  female,  1.5  mm.;  of  male,  1.3  mm."* 
Marsh  states,  in  connection  with  the  original  description, 
that  the  material  in  which  this  species  was  found — collected 
by  Professor  Birge  at  New  Lisbon,  Wisconsin — contained  only 
a  few  individuals,  and  that  his  own  search  for  it  in  other 
Wisconsin  localities  had  been  unsuccessful.  He  says  also 
that  the  species  resembles  the  European  species  D.  gracilis 
more  closely  than  any  other  American  form. 

The  description  quoted  above  is  the  only  literature  on  the 
subject,  and  while  a  request  for  slides  or  specimens  of  the 
species  by  Professor  Marsh  was  kindly  complied  with  in  the 
case  of  most  of  his  species,  to  his  own  as  well  as  my  regret 
he  was  unable  to  let  me  have  either  slides  or  specimens  of  D. 
birgei. 

Unfortunately, as  Marsh  says,  but  few  specimens  were  found, 
and  further  study  of  the  species  must  consequently  be  deferred 
until  later  collections  shall  afford  an  opportunity. 

Diaptomus  mississippiensis  Marsh.    (PL  XXXIII.,  Fig. 
1-4.) 

Diaptomus  mississippiensis,  Marsh,  '94,  p.  15,  PJ.  I.,  Fig.  1-3. 
Diaptomus  mississippiensis,  Herriok  and   Turner,  '95,  p.  78,  PI. 
XLVIL,  Fig.  1-3. 

A  medium-sized  species.  Body  slender,  widest  about  the 
middle  of  the  posterior  third,  the  male  a  little  more  slender 
than  the  female,  and  the  widest  part  slightly  farther  forward. 
Last  two  cephalothoraic  segments  indistinctly  confluent; 
suture  between  the  first  two  distinct.  Last  cephalothoracic 
segment,  seen  from  above,  not  produced,  but  bearing  a 
minute  obtuse  spine  pointing  backward ;  seen  from  the  side 
it  is  broadly  rounded,  with  the  spine  in  the  middle,  giving  it 
the  form  of  a  brace  ( — 1 — .).  First  abdominal  segment  about 
as  long  as  the  remainder  of  the  abdomen  (PI.  XXXIII.,  Fig. 
4),  with  a  short  obtuse  spine  opposite  the  anterior  margin  of 


♦Description  quoted  from  Marsh,  '94. 


174     Illinois  State  Laboratory  of  Natural  History. 

the  receptaculum  seminis ;  the  second  segment  the  shortest ; 
third  segment  slightly  longer  than  the  second.  In  the  male 
(PL  XXXIII.,  Fig.  1)  there  is  little  difference  in  the  length 
of  the  abdominal  segments.  Furcal  rami  broad,  but  little 
longer  than  the  third  abdominal  segment ;  distinctly  hairy 
within.  Furcal  setae  thick  at  the  base,  tapering  gradually 
toward  the  tip;  distinctly  setose.  The  inner  furcal  seta  is 
smooth  in  both  sexes. 

Antennae  2 5 -segmented,  reaching  to  or  slightly  beyond  the 
tips  of  the  furcal  setae.  The  right  male  antenna  with  the  six 
segments  preceding  the  geniculation  greatly  swollen;  ante- 
penultimate article  unarmed;  segments  19,  20,  and  21,  also 
22  and  23  ankylosed. 

Fifth  pair  of  feet  of  the  female  (PL  XXXIII.,  Fig.  2)  of 
moderate  size.  First  basal  segment  trapezoidal,  the  longer 
base  forming  the  inner  margin.  Second  segment  of  the  outer 
ramus  long,  narrow,  acuminate,  shorter  than  the  preceding 
segment,  perfectly  smooth  within.  Third  segment  wanting ; 
represented  by  two  straight  and  pointed  spines,  an  inner  short 
one  and  an  outer  one  more  than  twice  as  long. 

Inner  ramus  of  fifth  foot  of  female  one-segmented,  reach- 
ing almost  to  the  middle  of  the  second  segment  of  the  outer 
ramus ;  distinctly  hairy  on  inner  margin  near  the  apex,  where 
it  is  armed  with  two  spines,  the  inner  one  being  fully  one 
third  as  long  as  the  ramus  itself. 

First  segment  of  outer  ramus  of  right  fifth  foot  of  male 
(PL  XXXIII.,  Fig.  3)  subquadrate,  slightly  longer  than  broad, 
the  second  segment  nearly  twice  as  long  as  the  first,  its  upper 
half  about  as  wide  as  the  first.  A  little,  below  the  middle  of 
this  segment  the  inner  margin  is  produced  into  a  short  spine- 
like process,  concave  toward  the  apex  of  the  segment.  Be- 
tween this  and  the  apex  the  segment  is  produced  into  a 
narrow,  triangular  hyaline  lamina,  tapering  from  the  broad 
upper  part  to  the  inner  apical  angle.  Marginal  spine  long 
and  curved,  concave  toward  the  apex  of  the  segment  and 
inserted  very  near  the  outer  apical  angle.  Terminal  hook 
long  and  very  slender,  with  two  sharp  angles  dividing  it 
approximately  into  thirds  ;   upper  third  rather  thick  as 


North  American  Species  of  Diaptomus.  175 


compared  with  the  remainder ;  lower  two  thirds  very  minutely 
spinose ;  tip  sometimes  slightly  recurved. 

Inner  ramus  of  right  fifth  foot  one -segmented,  narrowing 
but  slightly  toward  the  tip.  It  reaches  almost  to  the  middle 
of  the  last  segment  of  the  outer  ramus,  but  not  to  the  hook- 
like process.  Apex  rounded;  unarmed  or  very  delicately 
hairy. 

Outer  ramus  of  the  left  fifth  foot  two-segmented.  First 
segment  irregularly  trapezoidal;  small  and  inconspicuous, 
with  a  delicately  hairy  cushion-like  process  on  the  inner  mar- 
gin. Last  segment  consisting  of  two  digitiform  processes, 
forming  a  forcipate  structure.  Seen  from  behind,  the  upper 
process  is  smooth,  the  base  slightly  swollen.  It  is  a  little  longer 
than  the  other  and  about  one  and  a  half  times  as  long  as  the 
preceding  segment,  tapering  gradually  from  the  thickened 
part  to  an  obtuse  point.  The  lower  process  (seen  from  behind) 
is  about  equally  broad  at  the  base  and  at  the  beginning  of  the 
last  third,  whence  it  narrows  quite  suddenly  to  form  an  obtuse 
point.  It  is  provided  within  and  at  the  apex  with  four  or 
five  small  teeth. 

Inner  ramus  of  left  fifth  foot  paddle-shaped,  considerably 
broadest  at  the  apex  ;  reaching  almost  to  the  tip  of  the  outer 
ramus  ;  either  smooth  or  very  delicately  hairy. 

Length  of  female,  1.2  mm. ;  of  male,  1.1  mm. 

Most  of  the  specimens  examined  were  taken  from  Lake 
Maitland,  Florida,  from  material  kindly  loaned  me  by  Mr. 
Adolph  Hempel. 

The  above  was  prepared  as  a  description  of  a  new  species, 
but  when  I  saw  Professor  Marsh's  slides  there  was  no  longer 
any  doubt  as  to  the  identity  of  mississijijiiensis  and  this  Florida 
form.  Prof.  Marsh  ('94)  figures  the  furca  of  the  female  as 
perfectly  smooth  within,  while  in  all  of  the  specimens  from 
Florida,  as  well  as  in  those  which  he  kindly  loaned  me,  they 
are  distinctly,  though  not  heavily,  setose  within.  The  inner 
rami  of  the  fifth  pair  of  feet  in  the  male,  however,  differ  con- 
siderably— probably  a  varietal  difference,  since  in  a  few  of  my 
specimens  they  approached  the  form  shown  in  his  figures. 
In  the  Florida  specimens  I  fail  to  find  the  asymmetry  in  the 


176      Illinois  State  Laboratory  of  Natural  History. 

abdominal  spine  mentioned  by  Marsh,  but  since  the  speci- 
mens from  the  two  localities  differ  in  other  respects  it  is  not 
unlikely  that  this  difference  also  may  exist. 

Found  by  Professor  Marsh  in  collections  from  small  lakes 
and  ponds  In  Mississippi,  and  by  the  writer  in  material  col- 
lected from  a  number  of  Florida  lakes  in  March,  1896,  by 
Mr.  Adolph  Hempel.  Professor  Marsh  states  that  in  collec- 
tions made  in  Mississippi  in  January  and  February,  1893, 
D.  mississijijnensis  was  the  only  Diaptomus  found ;  but  in  the 
Florida  collections  this  species  occurred  in  connection  with 
D.  albuquerquensis  Herrick,  the  two  being  about  equal  in 
numbers.  In  general  appearance  these  two  species  are  very 
similar,  but  they  are  widely  different  in  the  details  of  their 
structure. 

Diaptomus  tyrrelli  Poppe. 

Diaptomus  tyrrelli,  Poppe,  '88,  p.  159. 

Diaptomus  tyrrelli,  de  Guerne  et  Richard,  '89b,  p.  39,  PI.  I.,  Fig. 
17, 18;  PI.  IV.,  Fig.  26. 

Diaptomus  fresnanus,  Lilljeborg,  in  litt* 

Diaptomus  tyrrelli,  Herrick  and  Turner,  '95,  p.  76,  PI.  X.,  Fig.  9. 

"Of  medium  size.  Cephalothorax  widest  at  the  middle 
and  at  the  lateral  lobes  of  the  last  segment.  Last  two  tho- 
racic segments  confluent  above,  and  the  last,  seen  from  above, 
produced  obliquely  into  large  lateral  processes,  almost  ovate, 
acuminate  posteriorly,  with  a  rather  large  mucro.  First 
abdominal  segment  almost  as  long  as  the  rest  of  the  abdomen, 
somewhat  dilated  anteriorly,  and  provided  with  long  mucro- 
nate  lateral  processes.  Second  and  third  abdominal  segments 
rather  short,  with  a  vestige  of  a  transverse  suture  anteriorly. 
Furcal  rami  short,  sparsely  hairy,  and  almost  one  and  a  half 
times  as  long  as  broad. 

"First  pair  of  antennae  in  the  female,  reflexed,  reach 
almost  to,  sometimes  to  the  end  of,  the  furca ;  composed  of 
twenty-five  segments.  Antepenultimate  article  of  the  pre- 
hensile antenna  of  the  male  wholly  unarmed,  or  mimrtely 
and  scarcely  perceptibly  armed. 


*  The  description  given  herewith  is  that  of  D.fresnanus  Lilljeborg,  sent  by  him 
to  de  Guerne  and  Richard,  and  published  by  them  under  the  name  of  D,  tyrrelli. 


North  American  Species  of  Diap.tomus. 


177 


"  Outer  ramus  of  the  fifth  pair  of  feet  in  the  female  Inarticu- 
late ;  unguiform  process  of  the  second  segment  almost  parallel 
to  the  first  segment,  slightly  curved  within  and  minutely  ciliate 
on  the  inner  margin,  the  last  cilia  spine-like.  Inner  ramus 
simple  and  slender,  about  equal  to  the  first  segment  of  the 
outer  ramus ;  armed  at  the  outer  margin  and  near  the  apex 
with  two  medium- sized  spines  ;  apex  obtuse  and  finely  hairy. 

"Eight  fifth  foot  in  the  male  slender  and  of  medium  size. 
First  segment  of  the  outer  ramus  with  a  small  hyaline  lamella 
near  the  inner  apical  angle.  Second  segment  comparatively 
small  and  strongly  curved  ;  the  outer  marginal  spine  at  about 
the  middle.  Terminal  hook  slightly  sigmoid ;  inner  margin 
smooth.  Inner  ramus  minute  and  simple,  not  reaching  the 
end  of  the  first  segment  of  the  outer  ramus. 

"  Second  segment  of  the  outer  ramus  of  the  left  foot  of  the 
same  pair  almost  triangular ;  inner  margin  slightly  sinuate 
and  ciliate  and  armed  with  two  obtuse  processes  (one  apical, 
the  other  lateral).  Inner  ramus  indistinctly  two-segmented 
extending  about  to  the  middle  of  the  second  segment  of  the 
outer  ramus  ;  minutely  hairy  within  and  at  the  apex. 

"Length  of  female  1.9  mm.;  of  male  1.8  mm."  # 

"  This  Diaptomusis  distinguished  from  all  its  related  forms 
by  the  large  lateral  lobes  of  the  last  thoracic  segment.  These 
lobes,  seen  from  above,  arc  acuminate,  but  seen  from  the  side, 
the  posterior  extremity  is  obtuse  and  armed  with  two  spines. 

"  The  first  abdominal  segment  is  remarkable  on  account  of 
its  long,  strong,  pointed  processes. 

"  The  female  of  this  species  slightly  resembles  />.  <tinhi<iiu<s 
Lillj.,  from  Behring  Isle,  but  the  lateral  projections  of  the 
first  abdominal  segment  are  wanting  in  the  latter.  I),  tyrrelli 
differs  from  most  other  American  species  in  the  absence  of  a 
prolongation  on  the  antepenultimate  article  of  the  male  pre- 
hensile antenna. 

"The  first  specimens  of  this  copepod  were  collected  in 
Summit  Lake,  in  the  Rocky  Mountains,  at  a  height  of  5,300 
feet,  and  sent  to  Herr  S.  A.  Poppe  by  Mr.  J.  B.  Tyrrell,  of 
Ottawa,  Canada. 


*Lilljeborg'B  description  from  do  Ouerne  et  Iticliard,  '89b. 


178     Illinois  State  Laboratory  of  Natural  History. 


"  The  description  given  was  sent  to  us  by  Prof.  Lilljeborg 
as  that  of  a  new  species  described  by  him  under  the  name  of 
D.  fresnanus.  It  was  established  from  specimens  found  by 
G.  Eisen  at  Centreville,  near  Fresno,  Cal.  D.  tyrrelli  here 
reaches  a  size  somewhat  greater  than  that  which  it  has  at 
Summit  Lake,  where  it  is  only  1.5  mm.  long."* 

Owing  to  the  kindness  of  Herr  Poppe  I  was  enabled  to  ex- 
amine specimens  of  Z).  tyrrelli,  but  found  nothing  to  add  to 
the  above  description.  I  failed  to  obtain  specimens  from  Dr. 
Lilljeborg,  and  so  am  unable  to  say  whether  or  not  there  are 
minor  differences  to  be  found  in  individuals  from  the  two 
localities  in  which  they  have  hitherto  been  found. 

Diaptomus  clavipes  n.  sp.     (PI.  XXXIV.,  Fig.  1-3  ;  PI. 
.    XXXV.,  Fig.  1,  2.) 

Body  of  about  the  same  width  throughout,  except  at  the 
head  and  at  the  last  thoracic  segment,  where  it  narrows 
slightly.  Last  two  thoracic  segments  confluent,  the  last  one 
with  slightly  rounded  posterior  angles,  armed  on  each  side 
with  a  short  blunt  spine.  In  the  male  the  body  is  less 
strongly  bifid  than  in  the  female,  and  the  spines  are  smaller. 
There  is  but  slight  difference  in  the  length  of  the  abdominal 
segments  (PI.  XXXV.,  Fig.  2),  the  second  segment  being- 
longest  and  about  equal  to  the  furcal  rami.  The  first  seg- 
ment is  asymmetrical  and  armed  on  each  side  with  a  thick 
blunt  spine,  the  one  on  the  right  side  being  the  more  conspic- 
uous ;  in  the  male  the  segment  is  unarmed.  Furcal  rami  hairy 
within ;  furcal  setre  long,  slender,  and  covered  with  delicate 
hairs. 

Antennae  25-segmented,  extending  beyond  the  furcal  seta^. 
Geniculate  antenna  of  the  male  (PI.  XXXIV.,  Fig.  2)  greatly 
swollen  from  the  twelfth  to  the  eighteenth  segments  inclusive. 
The  armature  of  the  segments  is  as  follows :  1  and  7  have  a 
sense-club  and  a  long  spine  ;  2,  two  long  spines,  a  sense-club, 
and  a  sense-hair;  3,  a  sense-club  and  a  long  seta;  4  and 
8,  a  long  spine;  5,  a  sense-club  and  a  short  seta;  8,  a 
short  and  a  long  spine;  9,  a  short  spine,  a  long  seta,  and  a 


*l)e  Guerne  el  Kichard,  '89b. 


NortJi  American  Species  of  Diaptomus.  179 


sense-club;  10  and  11,  two  long  spines,  one  much  thicker 
than  the  other,  and  a  process;  12,  a  long  spine,  a  short 
spine,  and  a  sense-club ;  13,  a  long  spine  and  a  process  ;  14, 
a  long  spine,  a  long  seta,  and  a  sense-club;  15,  a  process, 
a  long  spine,  a  short  seta,  and  a  sense-club;  16,  a  process,  a 
long  spine,  a  long  seta,  and  a  sense-club  ;  17,  a  plate-like  proc- 
ess, a  long  and  a  short  spine  ;  18,  a  plate  and  a  short  spine  ; 
19,  20,  and  21  (usually  completely  ankylosed  but  some- 
times with  sutures  indistinctly  visible),  a  very  long  spine,  a 
long  seta,  and  a  short  cuticular  process;  22  and  23  (com- 
pletely ankylosed),  a  narrow  hyaline  lamina  (bisected  by  a 
sense  hair)  and  two  setae ;  24,  two  setae;  and  25,  two  long 
setae  and  two  short  ones,  a  sense  hair,  and  a  sense-club. 

Fifth  pair  of  feet  in  the  male  (PI.  XXXV.,  Fig.  1)  charac- 
teristic. First  basal  segment  of  the  right  leg  produced  at  the 
inner  apical  angle  into  a  process  (generally  blunt  but  some- 
times spine-like)  having  on  the  posterior  surface  a  tubercle 
bearing  a  short  blunt  spine.  Second  basal  segment  (PI. 
XXXIV.,  Fig.  1)  armed  at  the  inner  margin  with  two  proc- 
esses, the  proximal  one  broad,  prominent,  concave  toward 
the  apex  of  the  segment ;  the  other,  slightly  above  the  middle 
of  the  segment,  a  mere  sharp  triangular  point.  At  the  outer 
apical  angle  is  a  slight  indentation  from  which  springs  a  del- 
icate hair,  and  from  the  inner  apical  angle  arises  the  inner 
ramus.  First  segment  of  the  outer  ramus  irregular,  about 
one  and  a  half  times  as  long  as  broad,  with  a  small  sharp  tri- 
angular point  on  the  inner  margin  at  about  the  -beginning  of 
the  distal  fifth.  On  this  segment  is  a  structure  which  is  not,  to 
my  knowledge,  found  in  any  other  Diaptomus.  This  is  a  hook 
arising  from  the  middle  of  the  posterior  aspect,  and  reaching 
to  the  end  of  the  segment.  It  is  sickle-shaped,  perfectly 
smooth,  and  although  supplied  with  muscles  does  not  seem  to 
be  movable.  Second  segment  subquadrate,  about  twice  as  long- 
as  wide.  The  marginal  spine  is  short,  almost  straight,  about 
a  third  the  length  of  the  segment, delicately  serrate  within.  Ter- 
minal hook  very  stout,  as  long  as  the  two  preceding  segments, 
tapering  gradually,  and  slightly  recurved  at  the  tip  ;  armed  for 
the  distal  two  thirds  of  the  inner  margin  with  strong  teeth. 


180     Illinois  State  Laboratory  of  Natural  History. 

Inner  ramus  of  the  right  fifth  foot  short,  about  the  same 
breadth  throughout,  almost  reaching  the  middle  of  the  first 
segment  of  the  outer  ramus ;  armed  at  the  tip  with  a  number 
of  strong  blunt  spines. 

Second  basal  segment  of  the  left  fifth  leg  subquadrate,  the 
inner  margin  distinctly  tuberculate,  the  outer  apical  angle 
with  a  delicate  hair.  First  segment  of  the  outer  ramus  sub- 
quadrate,  about  a  fourth  longer  than  broad ;  provided  at  the 
inner  margin  with  a  narrow  hyaline  lamina,  produced  at  the 
inner  apical  angle  into  a  delicately  hairy  cushion-like  process. 
The  second  segment  is  narrow,  about  half  as  broad  as  the 
preceding ;  delicately  hairy  within,  and  produced  at  the  inner 
distal  angle  into  a  cushion-like  process  densely  covered  with 
minute  hairs.  On  the  posterior  side  of  this  segment  are  two 
processes  :  one  a  long  straight  spine,  more  than  half  as  long 
as  the  segment  itself  and  armed  at  the  inner  margin  with 
very  strong  hairs  or  spinules,  largest  at  the  base  and  decreas- 
ing in  size  toward  the  tip ;  the  other  a  short,  thick,  blunt 
process,  perfectly  smooth,  about  a  third  the  length  of  the 
spine. 

Inner  ramus  of  left  fifth  leg  very  long  and  narrow,  arcuate 
(the  concavity  toward  the  outer  ramus),  about  one  eighth  as 
broad  as  long,  reaching,  beyond  the  end  of  the  first  and  almost 
to  the  middle  of  the  second  segment  of  the  outer  ramus.  It 
is  broadest  at  the  base  and  at  the  apex,  armed  at  the  tip  with 
a  number  of  strong  blunt  spinules,  and  tuberculate  its  entire 
length. 

Second  basal  segment  of  the  fifth  pair  of  feet  in  the  female 
(PI.  XXXIV.,  Fig.  3)  trapezoidal,  with  the  longest  base  form- 
ing the  inner  margin.  From  the  outer  margin  springs  the 
usual  delicate  hair.  The  first  segment  of  the  outer  ramus  is 
subquadrate,  not  quite  twice  as  long  as  broad.  Second  seg- 
ment subconical,  almost  straight,  a  little  shorter  than  the 
preceding  segment ;  the  third  segment  wanting,  represented 
by  two  sharp  slender  spines,  the  outer  more  than  twice  as 
long  as  the  inner. 

Inner  ramus  of  fifth  foot  of  female,  one-segmented,  longer 
than  the  first  segment  of  the  outer  ramus  and  of  uniform 


North  American  Species  of  Diaptomus.  181 


width ;  delicately  hairy  both  within  and  without ;  apex 
bluntly  rounded  and  armed  with  two  spines,  the  inner  long, 
sharp,  sinuously  curved,  the  outer  also  sharply  pointed  but 
only  about  half  as  long  as  the  inner. 

Length  of  female,  1.37  mm.;  of  male,  1.28-1.68  mm. 

Found  (not  very  abundantly)  in  material  from  West  Oko- 
boji  Lake,  Iowa,  very  kindly  loaned  me  by  Prof.  L.  S.  Eoss, 
of  Drake  University,  Des  Moines,  Iowa. 

This  species  is  very  similar  to  Dr.  Forbes's  D.  piscina  and 
D.  lej)topus,  but  the  details  of  structure  will  serve  at  once  to 
distinguish  it  from  them.  The  hook  on  the  first  segment  of 
the  right  fifth  foot  of  the  male  is  very  characteristic,  as  are 
also  the  processes  on  the  inner  margin  of  the  second  basal 
segment  of  the  same  leg.  D.  clavipes  offers  such  a  mass  of 
peculiar  details  that  it  is  distinguished  with  ease  from  all 
other  species  heretofore  described. 

The  name  clavipes  was  chosen  because  of  the  club-like 
inner  rami  of  the  fifth  pair  of  legs  of  the  male,  the  inner  ramus 
of  the  left  leg  especially  resembling  an  Indian  war- club. 

A  very  curious  fact  in  regard  to  the  distribution  of  this 
species  was  noted.  East  and  West  Okoboji  lakes  are  united 
by  a  very  deep,  somewhat  narrowed  channel,  but  are  so  nearly 
one  lake  that  no  account  of  the  division  is  taken  by  Rand  & 
McNally  in  their  atlas.  Although  there  is  nothing  whatever 
to  hinder  free  migration  from  one  part  of  the  lake  to  the 
other,  not  an  individual  was  found  in  material  from  E. 
Okoboji,  taken  the  same  day  and  under  the  same  circum- 
stances as  that  from  W.  Okoboji  in  which  the  specimens 
were  found. 

SPECIES  INSUFFICIENTLY  DESCRIBED. 

Diaptomus  caroli  Herrick. 

Diaptomus  oaroli,  Ilerriek  and  Turner,  '95,  p.  G9. 

This  species  name  occurs  once  in  the  description  of  I>.  sici- 
loides  (Herrick  and  Turner '95),  but  although  I  have  searched 
diligently  in  Herrick's  writings  for  an  original  description  or 
even  a  previous  reference  to  this  species,  I  have  been  unable 


182      Illinois  State  Laboratory  of  Natural  History. 


to  find  a  word  in  addition  to  the  following.  Speaking  of  D. 
siciloides,  he  says:  "This  species  approaches  D.  sicilis 
Forbes  and  D.  caroli  Herrick  very  closely,  and  is  said  also  to 
resemble  D.  gracilis  Sars.  From  caroli  it  may  be  at  once  dis- 
tinguished by  reason  of  the  fact  that  the  third  joint  of  the 
outer  ramus  of  the  fifth  foot  of  the  female  is  obsolescent." 
The  "  D.  caroli  Herrick"  would  lead  one  to  suppose  that  it 
had  been  described  before ;  but,  although  this  work  contains 
the  names  and  short  descriptions  of  all  the  other  species,  D. 
caroli  is  not  among  them.  I  doubt,  therefore,  whether  I  am 
justified  in  putting  it  even  under  the  head  of  "  insufficiently 
described  "  species. 

Diaptomus  longicornis  var.  similis  Herrick. 

Diaptomus  longicornis  var.  similis,  Herrick,  1884,  p.  141,  PI.  Q,  Fig. 
5-7. 

Diaptomus  similis,  Herrick  and  Turner,  '95,  p.  58. 

Something  has  already  been  said  in  regard  to  this  doubtful 
species  under  the  head  of  D.  leptopus.  First  mentioned  in 
Herrick's  "Final  Keport,"  as  one  of  two  varieties, — the  other 
being  the  true  leptopus  as  acknowledged  by  him  ('95a),— it 
is  not  mentioned  again  except  in  the  description  of  D.  fronds- 
canus,  where  he  says  "  The  form  of  the  fifth  feet  chiefly  sepa- 
rates this  species  from  Diaptomus  similis  Herrick."  This 
species  cannot  stand  until  a  more  complete  description  is 
written. 

DISTRIBUTION  OF  THE  AMERICAN  SPECIES  OF  DIAPTOMUS. 

D.  sicilis  Forbes  is  one  of  the  most  common  species  in  the 
Great  Lakes,  and  has  been  found  in  Wisconsin,  Michigan, 
Minnesota,  and  Yellowstone  Park.  In  Illinois  it  is  recorded 
from  Cedar  Lake  and  Fox  Lake. 

D.  piscines  Forbes  has  been  recorded  only  from  Yellowstone 
Park,  and  I  now  add  Portage  Slough,  Manitoba,  Can. 

D.  lintoni  Forbes  has  been  found  only  in  Yellowstone 
Park. 

I),  leptopus  Forbes  is  found  in  Massachusetts,  Wisconsin, 
Minnesota,  and  Illinois. 


North  American  Species  of  Diaptomus. 


183 


I),  sanguineus  Forbes  is  very  common  throughout  central 
and  southern  Illinois,  and  has  been  recorded  from  New  York, 
Wisconsin,  Minnesota,  and  Alabama. 

D.  stagualis  Forbes  is  also  a  common  species,  and  is  re- 
corded from  Minnesota,'  Illinois,  Ohio,  Kentucky,  and  Ala- 
bama. 

D.  shoshone  Forbes  has  never  been  found  outside  of  Yellow- 
stone Park. 

D.  pallidus  Herrick  is  an  exceedingly  common  species  in 
central  Illinois  and  has  been  recorded  from  Ohio,  Wisconsin, 
and  Minnesota. 

D.  albuquerquensis  Herrick  was  first  described  from  Albu- 
querque, N.  M.,  and  is  also  found  in  Florida. 

D.  novamexicanus  Herrick  has  only  been  recorded  from 
Albuquerque,  N.  M. 

I).  oregonensis  Lilljeborg  is  a  very  common  species  in  Illi- 
nois, occurring  generally  with  J),  siciloides  Lillj.  and  D.  palli- 
dus Herrick.  It  is  also  common  in  Wisconsin  and  is  found 
in  Michigan,  Minnesota,  and  Oregon. 

D.  siciloides  Lilljeborg  is  found  in  immense  numbers  at 
Havana,  111.  I  have  found  it  also  in  Iowa  and  Indiana  col- 
lections, and  it  was  originally  described  from  L.  Tulare, 
Fresno,  Cal. 

D.minutus  Lilljeborg  is  probably  the  common  species  in 
the  northern  tier  of  states.  It  has  been  found  in  Yellowstone 
Park,  in  the  Great  Lakes,  and  in  Wisconsin,  Michigan, 
Newfoundland,  Greenland,  and  Iceland. 

J),  franciscanus  Lilljeborg  has  been  found  only  by  G. 
Eisen,  near  San  Francisco,  Cal. 

P.  eiseni  Lilljeborg  is  also  a  California  species. 

P.  signicauda  Lillj.,  one  of  the  most  peculiar  of  American 
species,  is  recorded  only  from  the  Sierra  Nevadas. 

1>.  trybomi  Lilljeborg  is  recorded  only  from  Multnomah 
Falls,  Oregon. 

I),  ashlandi  Marsh  seems  to  be  the  most  widely  distributed 
of  American  forms,  having  been  found  in  the  Great  Lakes, 
in  Indiana,,  Michigan,  Wisconsin,  Oregon,  Idaho,  Washing- 
ton, and  in  Yellowstone. Park. 


184     Illinois  State  Laboratory  of  Natural  History. 


D.  reighardi  Marsh  has  been  recorded  only  from  New 
Lisbon,  Wisconsin. 

D.  mississippiensis  Marsh  is  common  in  Mississippi,  and 
has  been  found  in  Florida  in  connection  with  D.  albuquerquen- 
sis  Herrick. 

D.  tyrrelli  Poppe  was  described  by  the  author  of  the  species 
from  Summit  Lake,  and  by  Lilljeborg,  under  the  name  D. 
fresnanus,  from  Fresno,  near  Centreville,  Cal. 

D.  clavipes  n.  sp.  is  described  in  this  paper  from  West 
Okoboji  Lake,  Iowa. 


North  American  Species  of  Diaptomus.  185 


GENEKAL  BIBLIOGKAPHY*  OF  THE  GENEKA  DIAP- 
TOMUS, EPISCHUKA,  LIMNOCALANUS, 
AND  OSPHKANTICUM. 

This  bibliographical  list  has  been  prepared  principally  in  further- 
ance of  Dr.  Schmeil's  purpose  to  compile  a  complete  bibliography  of 
the  Copepocla  of  the  world.  To  this  end  the  list  published  by  him  in 
his  Monograph  (Schmeil,  '96)  has  been  critically  reviewed  and  in  some 
instances  corrected,  and  a  number  of  additions  have  been  made.  New- 
species  described  since  the  publication  of  de  Guerne  and  Richard's 
Revision  ('89b)  are  noted  in  connection  with  the  articles  containing  the 
original  descriptions. 

All  articles  except  those  marked  with  an  asterisk  are  in  the  library 
of  the  Illinois  State  Laboratory  of  Natural  History  or  in  that  of  the 
University  of  Illinois. 

Apstein,  C. 
'92.    (See  Article  II.) 

'96.  Das  Siisswasserplankton.  Methode  und  Resultate  der  quantita- 
tiven  Untersuchung.  201  pp..  113  Abbild.,  5  Tab.  Kiel  u.  Leipzig. 
Review,  Zool.  Centralbl.,  III.  Jahrg.,  No.  22.  pp.  764-769. 

Aurivillius,  C.  W.  S.,  u.  Cleve,  P  T. 
'96.    Das  Plankton  des  Baltischen  Meeres.    Bihang  till  K.  Svenska 
Vet.-Akad.  Handl.,  Bd.  X  X  L,  Afd.  IV.,  No.  8,  pp.  1-83,  Taf.  L,  II.; 
Abstract,  Zool.  Centralbl.,  IV.  Jahrg.,  1897,  No.  16,  pp.  546-550. 

Baird,  W. 
'50.    (See  Article  II.) 

Barrois,  Th. 

'91.    Sur  trois  Diaptomus  nouveaux  des  environs  du  Caire.  R6v. 

Biol,  du  Nord  de  la  France,  T.  111.,  Nos.  6,  7,  8. 
*'95.    Contribution  a  lV-tiide  de  quelques  lacs  de  Syrie.    Rev.  Biol. 

du  Nord  de  la  France,  T.  VI.,  No.  6.  pp.  221-240;  Abstract,  Biol. 

Central!)]..  X  Y.  Bd.,  Nr.  24,  pp.  869-S73. 
*'96.    Recherches  sur  la  faune  des  eaux  douces  des  Agores.  Mem. 

Soc.  sci.,  agr.,  arts,  Lille,  Ser.  V.,Fasc.  VI.  172  pp.,  3  cartes;  Abstract, 

Zool.  Centralbl.,  III.  Jahrg.,  No.  18,  pp.  609-611. 

Birge,  E.  A. 

'95.  On  the  Vertical  Distribution  of  the  Pelagic  Crustacea  of  Lake 
Mendota,  Wis.,  during  .Inly,  1894.  Biol.  Centralbl.,  XV.  Bd.,  Nr.  9, 
pp.  353-355. 

*As  the  bibliographical  list  published  in  connection  with  the  preceding  paper, 
Article  II.  of  this  series,  contains  a  large  number  of  titles  identical  with  those  of  this 
bibliography,  these  duplicate  titles  are  not  reprinted  here,  but  reference  is  made, 
under  the  author's  name  and  the  year  of  publication,  to  the  bibliographical  list  of  the 
preceding  article.— S.  A.  Fohbes. 


186      Illinois' State  Laboratory  of  Natural  History. 


'95a.  Plankton  Studies  on  Lake  Mendota.  I.  The  Vertical  Distri- 
bution of  the  Pelagic  Crustacea  during  July,  1894.  Trans.  Wis. 
Acad.  Sci.,  Arts,  and  Letters,  Vol.  X.,  pp.  421-184,  Pis.  VII.-X. 

'95b.  Turkey  Lake  as  a  Unit  of  Environment,  and  the  Variation  of 
its  Inhabitants:  Cladocera.f  Proc.  Ind.  Acad.  Sci.,  1895,  No.  5. 
p.  245. 

'97.  The  Vertical  Distribution  of  the  Limnetic  Crustacea  of  Lake 
Mendota.    Biol.  Centralbl.,  XVII.  Bel.,  Nr.  10,  pp.  371-375. 

B  lan  chard,  R. 

'90.  Sur  une  matiere  colorante  des  Diaptomus,  analogue  a  la  carotine 
des  vegetaux.  Compt.  Rend,  de  l'Acad.  des  Sci.,  Paris,  T.  CX.,  pp. 
292-294. 

'90a.  Sur  une  carotine  d'origine  animale,  constituant  le  pigment 
rouge  des  Diaptomus.  Mem.  de  la  Soc.  zool.  de  France,  T.  III., 
p.  113. 

Blanchard,  R.,  et  Richard,  J. 
'90.    (See  Article  II.) 
'91.    (See  Article  II.) 

'97.  Sur  la  faune  des  lacs  eleves  des  Hautes-Alpes.  Mem.  de  la  Soc. 
zool.  de  France,  T.  X.,  pp.  43-61. 

Brady,  G.  S. 
'68.    (See  Article  II.) 
'78-'80.    (See  Article  II.) 

'86.    Notes  on  Fresh-water  Entomostraca  from  South  Australia. 

Proc.  Zool.  Soc.  London,  1886,  pp.  82-84.   3  Pis.  • 
'86a.    Notes  on  Entomostraca  collected  by  Mr.  A.  Haley  in  Ceylon 

Journ.  Linn  Soc.   London,  Zool.,   Vol.  XIX.,  pp.  293-317,  PI. 

XXXVII.,  Fig.  21-26. 
'91.    (See  Article  II.) 
Buchholz,  R. 

*'74.  Crustaceen.  Die  zweite  deutsche  Nordpolfahrt  in  den  Jahren 
1869  u.  1870,  Bd.  II.,  pp.  262-398.   15  Pis. 

Bundy,  F.  W. 

'82.  A  List  of  the  Crustacea  of  Wisconsin.  With  Notes  on  some 
New  or  Little-known  Species.  Trans.  Wis.  Acad.  Sci.,  Arts,  and 
Letters,  1877-81,  Vol.  V.,  pp.  176-184. 

Cajander,  A.  H. 

'69.  Bidrag  till  kiinnedom  om  sydvestra  Finlands  Krustaceer.  Not. 
Sallsk.  pro  Fauna  et  Flora  Fennica  Forh.,  Heft  X.,  pp.  373-376. 


tReference  to  Diaptomus  and  to  Epischura  lacustris- 


North  American  Species  of  Diaptomus.  187 


Chambers,  V.  T. 

'81.  Two  New  Species  of  Entomostraea.  Journ.  Cincinnati  Soc.  Nat. 
Hist.,  Vol.  IV.,  pp.  47,  48.    2  Pis. 

Chyzer,  C. 

'58.  Uber  die  Crustaceenfauna  Ungarns.  Verh.  d.  K.-K.  zool.-bot. 
Gesellsh.  Wien,  Bd.  VI1L,  p.  505. 

Claus,  C. 
'58.    (See  Article  II.) 
'63.    (See  Article  II.) 
'76.    (See  Article  II.) 

*'77.  Die  Schalendrtise  der  Copepoden.  Sitzungsber.  Akad.  Wien, 
Math.  Nat.  CI.,  LXXIV.  Bd..  I.  Abth.,  pp.  717-721.    1  PI. 

'88.  tiber  den  Organismus  der  Nebaliden  und  die  systematische 
Stellung  der  Leptostraken.f  Arb.  zool.  Inst.  Univ.  Wien,  V1TI.  Bd., 
pp.  1-148,  Taf.  I.-XV. 

'93.    (See  Article  II.) 

'93a.    (See  Article  II.,^3b.) 

'93b.    (See  Article  II.,  '93c.) 

'95.  tiber  die  Wiederbelebung  im  Schlamme  eingetrockneter  Copep- 
oden und  Copepoden-Eier.  Zugleich  ein  Beitrag  zur  Kenntniss  von 
Microcyclors  diaphanus  (Fiscb.)  =  minutus  (Cls.).  Arb.  Zool.  Inst. 
Univ.  Wien,  T.  XL,  1  Heft,  pp.  1-11,  Taf.  I.,  II. 

'95a.  tiber  die  Maxillarfiisse  der  Copepoden  und  die  morphologi- 
sche  Deutung  der  Cirripedien-Gliedmassen.  Arb.  Zool.  Inst.  Univ. 
Wien,  T.  XI.,  1  Heft,  pp.  49-G3,  Taf.  VIII. 

Cragin,  F.  W. 
'83.    (See  Article  II.) 

Daday,  E.  v. 

'84.  Catalogue  Crustaceorurn  faun;*'  Transylvania1,  (e  collectione 
Musci  t  ransylvanici,  collegitet  determinavit).  [Latin  title  of  Hun- 
garian article.]  Orv.  Termeszettud.  Ertesito,  Vol.  IX.,  pp.  161—187 

'85.    (See  Article  II.,  85a.) 

'85a.    I'jallatfajok  Budapest  edesvi'zi  faunajabol.    Term,  fiiz.,  Vol. 

IX.,  p.  127,  PI.  XI. 
'85b.    (See  Article  II.,  '85.) 

*'90.    Conspectus  Diaptoinorum  fauna'  hungarica'.    Math,  naturw. 

Berichte  a.  Ungarn,  Bd.  XIII.,  pp.  114-143,  Pis.  IV.-V1. 
*'90a.    Ubersicbt  der  I  Haptonms-Arten  Ungarns.     Math,  naturw. 

Berichte  a.  Ungarn,  Bd.  XIV.,  pp.  177-1S0. 


tKutterung  mil  Karbstort'en  an  Diaptomus,  pp.  99,  101. 


188      Illinois  State  Laboratory  of  Natural  History. 


'91.  Adatok  Magyarorszag  edesvi'zi  mikroskopos  faumvjanak  isme- 
retehez.  Term  fiiz.,  Vol.  XIV.,  pp.  16-31,  PI.  I.  Also  in  German: 
Beitriige  zur  Mikropischen  Siisswasserfauna  Ungarns,  Ibid.,  pp.  107- 
123. 

'91a.  Az  edclig  pontosan  ismert  Diaptomus-fajok  meghatarozo  tab- 
lazata.  Tabella  synoptica  specierum  generis  Diaptomus  hucusque 
recte  cognitarum.  [Article in  Hungarian  and  Latin.]  Term,  fiiz., 
Vol.  XIV.,  pp.  32-51. 

'97.  Beitrage  zur  Kenntniss  der  Microfauna  der  Tatra-Seen.  Term, 
fiiz.,  Vol.  XX.,  pp.  149-196. 

Dahl,  Fr. 

*'94.    Die  Copepodenfauna  des  unteren  Amazonas.    Ber.  d.  naturf. 

Gesellseh.  zu  Freiburg,  i.  B.,  Bd.  VIII.,  pp.  10-23,  Taf.  I.,  Fig.  1-4. 
Diaptomus  kensenii  n.  sp. 
'95.    Neueres  iiber  Morphologie  und  Ethologie  der  Copepoden.  Zool. 

Centralbl.,  II.  Jahrg.,  No.  22  u.  23,  pp.  673-678. 

De  Kay,  J.  E.  m 
'44.    Crustacea.   Nat.  Hist.  New  York,  Zoology,  Part  VI.,  pp.  1-65. 
Pis.  I.-XI1I. 

Eusebio,  J.  B. 

'88.  Recherches  sur  la  faune  des  eaux  du  Plateau  Central.  La  Faune 
pelagique  des  lacs  d'Auvergne.  Rev.  d'Auvergne  (Clermont-Fer- 
rand) [Fide  Schmeil].    Separate,  pp.  1-29,  PI.  L,  Fig.  10. 

Fellows,  C.  S. 

'87.  A  description  of  Ergasilus  chautauquaensis,  a  New  Species  of 
Copepoda,  and  a  List  of  other  Entomostraca"found  at  Lake  Chau- 
tauqua in  August,  1886.  Proc.  Am.  Soc.  Microscopists,  1887.  4  pp., 
1  PI. 

Ferussac,  D.  de 

*'06.  Memoire  sur  cleux  nouvelles  especes  d'Entomostraces  et  d'Hy- 
drachnes  (Cyclops  mailer i\_=  Diaptomus  cceruleus]  and  Cypris  renifor- 
mis).    Ann.  Mus.  hist,  nat.,  T.  VII.,  p.  213. 

Fischer,  S. 

*'51.  Beitrage  zur  Kenntniss  der  in  der  LTmgegencl  von  St.  Peters- 
burg sich  findenden  Cyclopiden.  Bull.  Soc.  Imp.  des  Naturalistes 
de  Moscou,  T.  XXIV.,  Pt.  II.,  pp.  409-438,  Pis.  IX.,  X. 

*'53.  Beitrage  zur  Kenntniss  der  in  der  Umgegend  von  St.  Petersburg 
sich  findenden  Cyclopiden.  Fortzetzung.  Bull.  Soc.  Imp.  des  Nat- 
uralistes de  Moscou,  T.  XXVI.,  Pt.  II.,  No.  1,  pp.  74-100,  Pis. 
II.,  III. 

Forbes,  S.  A. 
'76.    (See  Article  II.) 


North  American  Species  of  Diaptomus. 


189 


'78.    The  Food  of  Illinois  Fishes.    Bull.  111.  State  Lab.  Nat.  Hist., 

Vol.  I.,  No.  1,  pp.  71-89. 
'78a.    On  the  Crustacea  eaten  by  Fishes.   Bull.  111.  State  Lab.  Nat. 

Hist,  Vol.  I.,  No.  2,  p.  87. 
'80.    The  Food  of  Fishes.    Bull.  111.  State  Lab.  Nat.  Hist.,  Vol,  I., 

No.  3,  pp.  18-65;  Rep.  111.  State  Fish  Comm.,  1884,  pp.  90-127. 
'80a.    On  the  Food  of  Young  Fishes.    Bull.  111.  State  Lab.  Nat.  Hist., 

Vol.  I.,  No.  3,  pp.  66-79. 
'82.    On  the  First  Food  of  the  Young  White  Fish.   American  Field, 

Mar.  11, 1882. 
'82a.    (See  Article  II.) 
'82b.    (See  Article  II., '82.) 

'83.  The  Food  of  the  Smaller  Fresh-water  Fishes.  Bull.  111.  State  Lab. 
Nat.  Hist.,  Vol.  I.,  No.  6,  pp.  65-95;  Rep.  Bd.  111.  State  Fish.  Comm., 
1886,  pp.  114-138. 

'83a.    The  First  Food  of  the  Common  White-Fish  (Coregonus  clupei- 
formis  Mitch.).    Bull.  111.  State  Lab.  Nat.  Hist.,  Vol.  1.,  No.  6,  pp. 
95-109;  Rep.  Bd.  111.  State  Fish  Comm.,  1886,  pp.  139-149. 
'87.    (See  Article  II.) 
'90.    (See  Article  II.  '90a.) 
'90a.    (See  Article  II.  '90.) 
'93.    (See  Article  II.) 
Forel,  A.  F. 

'78.  Faunistische  Studien  in  den  Siissvvasserseen  der  Schweiz.  Zeit- 
schr.  f.  wiss.  Zool.,  Bd.  XXX.,  Suppl.,  pp.  383-391. 

'82.  Die  pelagische  Fauna  der  Siissvvasserseen.  Biol.  Centralbl.,  II. 
Bd.,  Nr.  10,  pp.  299-305 ;  Translation,  Ann.  Mag.  Nat.  Hist.,  Vol.  X., 
p.  320. 

France,  It.  H. 

'94.  Zur  Biolo<»ie  des  Planktons.  Vorliiufige  Mitteilung.  Biol.  Cen- 
tralbl., XIV.  Bd.,  Nr.  2,  pp.  33-38. 

Fric  (Fritsch),  A. 
'72.    (See  Article  II.) 

'95.  Uber  Parasiten  bei  Crustaceen  und  Riiderthieren  der  siissen  Ge- 
wasser.  Bull.  Internat'n'l  d' Acad,  des  Sci.de  l'Empereur  Frangois 
Joseph  I ,  Classe  des  Sci.  Math,  et  Nat.,  pp.  1-7. 

'95a.    (See  Article  II.  95.) 

Fritsch  (Fric  ),  A.,  u.Vavra,  V. 
'92.    (See  Article  II.) 
'94.    (See  Article  II.) 


190     Illinois  State  Laboratory  of  Natural  History. 


Fric,  J.  A. 
'82.    (See  Article  II.) 

Gadeau  de  Kerville,  H. 
'88.    Les  Crustaces  de  la  Normandie:  espeees  fluviales,  stagnates  et 
terrestres;  premiere  liste.    Bull,  de  laSoc.  des  Amis  des  Sci.  nat.  de 
ttouen,  1888,  lre  Sem.,  pp.  133-158. 

Garbini,  A. 

'93.  Primi  Materiali  per  una  Monografia  Limnologiea  del  Lago  di 
Garda.  III.  Limnofauna.  Estr.  dal  Vol.  LXLX.,  Ser.  III.,  dell' 
Acead.  Agric.,  Arti,  e  Comm.  di  Verona,  pp.  28,  37,  49. 

'94.    (See  Article  II.) 

'95.    Fauna  Limnetica  e  Profonda  del  Benaco.    Boll.  Mus.  di  Zool. 

ed  Anat.  comp.  della  Univ.  di  Torino,  Vol.  X.,  Xo.  198,  pp.  2,  4,  5. 
'95a.    Appunti  di  Carcinologia  Veronese.  I.  Elenco  dei  Crostacei 

veronesi.    Estr.  dal  Vol.  LXXL,  Ser.  III.,  Fasc.  I.,  dell' Acead.  di 

Verona,  p.  3. 

'95b.  Appunti  di  Carcinologia  Veronese.  II.  Considerazione  ecolog- 
iehe  e  corologiche.  Estr.  dal  Vol.  LXXL,  Ser.  III.,  Fasc.  1,  dell' 
Acead.  di  Verona,  pp.  9,  14. 

'95c.  Distribuzione  e  Intensita  della  Fauna  atesina.  Estr.  dal  Vol. 
LXXL,  Ser.  III.,  Fasc.  II.,  dell'  Acead.  di  Verona,  p.  10. 

Gerst acker,  A. 

'54.  Bericht  iiber  die  Leistungen  in  der  Naturgeschichte  cler  Crusta- 
ceen,  Arachniden,  und  Myriapoden  wahrend  des  Jahres  1852  und 
1853.    Arch.  f.  Xaturgeseh.,  XX.  Jahrg.,  Bd.  2,-pp.  72-108. 

'63.    Copepoda.    Handbuch  der  Zoologie,  pp.  402,  403.  Leipzig. 

'66-'79.  Copepoda.  Bronn's  Klassen  und  Ordnungen  des  Thier- 
reichs,  V.  Bd.,  I.  Abtheil.,  pp.  590-806.  / 

Giesbrecht,  W. 

'81.  VorKiufige  Mitteilung  aus  einer  Arbeit  iiber  die  freilebenden 
Copepoden  des  Kieler  Hafens.  Zool.  Anz.,  XIV.  Jahrg.,  No.  83,  pp. 
254-258. 

'82.  Die  freilebenden  Copepoden  der  Kieler  Fohrde.  IV.  Ber.  d. 
Komm.  z.  w.Unters.  d.deutsch.  Meerein  Kiel,  pp.  87-1 G8,  Taf.  I-XII. 

'92.  Systematik  und  Faunistik  der  pelagischen  Copepoden  des  Golfs 
von  Xeapel  und  der  angrenzenden  Meeres-abschnitte.  XIX.  Mono- 
graph, der  Fauna  und  Flora  des  Golfs  von  Xeapel.  831  pp.,  54  Pis. 
Berlin. 

'93.  Mitteilungen  iiber  Copepoden.  G.  Zur  Morphologie  der  Mnxil- 
lipeden.  Mitteilungen  a.  d.  zool.  Stat,  zu  Xeapel,  Bd.  XI.,  Heft 
I.,  pp.  83-102. 


North  American  Species  of  Diaptomus.  191 


'95.  Mitteilungen  iiber  Copepoden.  7.  Zur  Morphologie  des  weib- 
lichen  Abdomens.  Mitteilungen  a.  d.  zool.  Stat,  zu  Neapel,  Bd. 
XI.,  Heft  IV.,  pp.  631-G48. 

Gissler,  C.  F. 

'81.  Variations  in  a  Copepod  Crustacean.  Am.  Nat.,  Vol.  XV.,  pp. 
639-G98. 

'81a.  Note  regarding  Change  of  Color  in  Diaptomus  sanguineus. 
Am.  Nat.,  Vol.  XV.,  p.  742. 

Grobben,  C. 

'80.  Die  Antennendrtise  der  Crustaceen.  Arb.  Zool.  Inst.  Univ. 
Wien,  Bd.  III.,  pp.  93-110,  Taf.  IX. 

'92.  Zur  Kenntniss  des  Stammbaumes  und  des  Sj'stems  der  Crusta- 
ceen. Sitzungsber.  der  K.  Akad.  der  Wissensch.  in  Wien,  Math.- 
naturw.  Classe,  Bd.  CI.,  Abt.  I.,  Jan.,'  1892,  pp.  1-38. 

Gruber,  Aug. 

'78.  tiber  Bildung  und  Wirkung  der  Spermatopboren  bei  Diaptomus 
gracilis  und  Heterocope  robusta.  Dissertation.  Promotionsschrift 
zur  Erlangung  der  Doktorwurde,  der  pbilosoph.  Facult.  der  Univ. 
Leipzig  vorgelegt.   34  pp.,  2  Pis.  Leipzig. 

'78a.  Die  Bildung  der  Eiersackchen  bei  den  Copepoden.  Zool.  Anz., 
I.  Jabrg.,  No.  11,  p.  247. 

Guerne,  J.  de 

'86.  Description  du  Centre-pages  grimaldii,  Copepode  nouveau  du 
goife  de  Finlande.  Bull,  de  la  Soc.  zool.  dc  France,  T.  XI.,  pp. 
276-285. 

'87.  Sur  les  genres  Ectinosoma  Boeck  et  Podon  Lilljeborg.  a  propos 
de  deux  Entomostraces  (Ectinosoma  atlanticwn  G.  S.  Brady  et  Kob- 
ertson,  et  Podon  minutus  G.  ().  Sars)  trouves  a  la  Corogne  dans 
l'estomac  des  sardines.f  liull.de  la  Soc.  zool.  de  France,  T.  XII., 
p.  29. 

Guerne,  Jul.  de,  et  Richard,  J. 

'88.   Sur  la  distribution  geographique  du  genre  Diaptomus.  Compt. 

rend,  dc  l'Acad.  des  Sci.,  2  juillet,  188S.  3  pp. 
'88a.    Diagnoses  dc  deux  Diaptomus  nouveaux  d'Algerie  (D.  hlan- 

chardi  et  D.  lilljeborgi).    Bull,  de  la  Soc.zool.de  France,  T.  XIII., 

pp.  K;U-l(i2. 
'89.    (See  Article  I  r., '89a.) 
'89a.    (See  Article  II.,  'SO.) 

'89b.  Revision  des  Calanides  d'eau  douce.  Mem.  de  la  Soc.  zool.  de 
France.  T.  II.,  pp.  53-181,  Pis.  1.-1V.  and  60  flg.  in  text. 


tReference  to  Limnocalanus  grimaldii. 


192     Illinois  State  Laboratory  of  Natural  History. 


'90.  La  distribution  geographique  des  Calanides  d'eau  douce.  Asso- 
ciation francaise  pour  l'avancement  des  sciences  fusionee  avec 
l'Assoe.  scient.  de  France,  Congres  de  Paris, Seance  du  14  aout,18S9. 
5  pp.,  1  PI. 

'90a.    Diagnose  d'un  Diaptomus  nouveau  du  Congo  (D.  loveni).  Bull. 

de  la  Soc.  zool.  de  France,  T.  XV.,  pp.  177, 178. 
'90b.    Description  du  Diaptomus  alluaudi  n.  sp.,  recueilli  par  M. 

Alluaud  dans  un  reservoir  d'eau  douce  a  Lanzarotte  (Canaries). 

Bull,  de  la  Soc.  zool.  de  France,  T.  XV.,  pp.  198-200. 
'90c.    On  the  Fresh-Water  Fauna  of  Iceland.   Ann.  and  Mag.  Nat. 

Hist,  Series  VI.,  Vol.  X.,  pp.  340-342. 
'91.    (See  Article  II.) 

'91a.    Synonymie  et  distribution  geographique  de  Diaptomus  alluaudi. 

Bull,  de  la  Soc.  zool.  de  France,  T.  X  VI.,  pp.  213-217. 
'91b.    (See  Article  II., '91a.) 

'91c.  Entomostraces  recueillis  par  M.  Charles  Raboten  Russie  eten 
Siberie  (Gouvernements  de  Kasau,  de  Perm,  de  Vologda,  et  de 
Tobolsk).   Bull,  de  la  Soc.  zool.  de  France,  T.  XVI.,  pp.  232-236. 

'92.  Sur  la  faune  des  eaux  douces  de  l'lslande.  Compt.  rend,  de 
l'Acad.  des  Sci.,  T.  CXIV.,  pp.  310-313. 

'92a.    (See  Article  II.) 

'92b.  Documents  nouveaux  sur  la  distribution  geographique  des 
Calanides  d'eau  douce.  Assoc.  franc,  pour  l'avane.  des  Sci.,  Con- 
gres de  Marseille,  1891,  T.  XX.,  Plate  V.    5  pp.  Paris. 

'92c.    (See  Article  II.,  '92b.) 

'93.    (See  Article  II.) 

*'94.    Diaptomus  chevreuxi,  Copepode  nouveau  d'Algerie.    Bull,  de  la 

Soc.  zool  de  France,  T.  XIX.,  p.  176. 
'96.    Premiere  liste  des  Copepodes  et  Cladoceres  d'eau  douce  du 

Portugal.    Bull,  de  la  Soc.  zool.  de  France,  T.  XXI.,  pp.  157-159. 
'96a.    D.  blanci,  Copepode  nouveau  recueilli  par  M.  Edouard  Blanc  a 

Boukhara  (Turkestan).    Bull,  de  la  Soc'  zool.  de  France,  T.  XXL, 

pp.  53-56.  5  Fig. 

Hacker,  F. 

*'95.  Die  Vorstadien  der  Eireifung.  Zusammenfassende  Unter- 
suchungen  iiber  die  Bildung  der  Vierergruppen  und  das  Verhalten 
der  kernblaschennucleolen.  Arch.  f.  mikr.  An  at'.,  Bd.  45,  pp.  200- 
273;  Abstract,  Zool.  Centralbl.,  II.  Jahrg.,  Nr.  18,  pp.  551-553. 

Hansen,  H.  J. 

'93.  Zur  Morphologie  der  Gliedmassen  und  Mundteile  bei  Crustaceen 
und  Insekten.  Zool.  Anz.,  XVI.  Jahrg.,  Nos.  420  u.  421,  pp.  193-198, 
201-212. 


North  American  Species  of  Diaptomus.  193 


Hartog,  M.  M. 

'80.    On  the  Anal  Respiration  of  the  Copepoda.  Quart.  Journ.  Micros. 

Sei.  London,  Vol.  XX.,  pp.  244-245;  Proc.  Manchester  Lit.  and 

Philos.  Soc,  Vol.  XIX.,  pp.  61,  G2. 
'82.    De  1'  ceil  impair  de3  Crustaces.    Compt.  rend.  Acad.  Paris,  T. 

XCIV.,  pp.  1430-1432;  Ann.  Mag.  Nat.  Hist.,  Vol.  X.,  pp.  71,72; 

Archiv  Zool.  Experim.,  Vol.  X.,  pp.  7,  8. 
'88.    (See  Article  II.) 

Hartwig,  W. 
'93.    (See  Article  II.) 
'94.    (See  Article  II.) 

'97.  Zur  Verbreitung  der  niederen  Crustaceen  der  Provinz  Bran- 
denburg. Forschungsber.  a.  d.  Biol.  Stat,  zu  Plon,  Theil  V.,  pp. 
115-149.  Stuttgart. 

Heller,  C. 

'71.    (See  Article  II.) 

Herrick,  C.  L. 

'77.    A  New  Cyclops.f  Geol.  and  Nat.  Hist.  Surv.  of  Minn.,  5th  Ann. 

Rep.,  pp.  238-239.    2  Figs. 
'79.    (See  Article  II.) 

'79a.  Fresh-water  En tomostraca.  Am.  Xat.,  Vol.  XIII.,  pp.  G20-629. 
4  Pis. 

'82.    (See  Article  II., '82a.) 
'83.    (See  Article  II.) 
'83a.    (See  Article  II.) 
'84.    (See  Article  II.) 
'87.    (See  Article  II.) 

'95.  Micro-Crustacea  from  New  Mexico.  Zool.  Anz.,  XVIII.  Jahrg., 
Nr.  4G7,  pp.  40-47.    2  Taf. 

[D.  alfmqtierquensis  and  D.  nommexicaiius.~\ 

Herrick,  C.  L.,  and  Turner,  C.  H. 
'95.    (See  Article  II.) 

Hoek,  P.  P.  C. 
'76.    (See  Article  II.) 

*'77-'78.  Zur  Entwickelungsgesehichte  der Entomostraken.  II.  Zur 
Embryologie  der  freilebenden  Copepoden.    Niedeii.  Arch.  f.  Zool. 
Bd.  IV.,  pp.  55-74,  Taf.  V.-VI. 
'78.    (See  Article  II.) 
Imhof,  O.  E. 

'83.    (See  Article  II.)  


fDisptomus  Bp.  .- 


194     Illinois  State.  Laboratory  of  Natural  History. 


'84.  Eesultate  meiner  Studien  iiber  die  pelagische  Fauna  kleiner 
und  grosserer  Siisswasserbecken  in  der  Sehweiz.  Zeitschr.  f.  wiss. 
Zool.,  Band  XL.,  pp.  154-178. 

'84a.    (See  Article  1L,  '84.) 

'85.    (See  Article  II.,  '85a.) 

'85a.    tiber  die  blassen  Kolben  an  den  vorderen  Antennen  der  Siiss- 

wasser-Calaniden.    Zool.  Anz.,  VIII.  Jahrg.,  Nr.  197,  p.  353. 
'85b.    (See  Article  II.,  '85.) 
'86.    (See  Article  II.) 
'86a.    (See  Article  II.,  *86b.) 

'87.  tiber  die  microscopische  Thierwelt  hochalpiner  Seen  (600- 
2780  m.  u.  M.).  Zool.  Anz.,  X.  Jahrg.,  Nos.  241  u.  242.  pp.  13-17, 
33-42  ;  Abstract,  Am.  Nat.,  Vol.  XXI.,  p.  G71. 

'87a.    (See  Article  II.) 

'87b.    (See  Article  II.) 

'88.    Fauna  der  Siisswasserbecken.    Zool.  Anz.,  XI.  Jahrg.,  Nos.  275 

ti.  276,  pp.  166-172,  185-190. 
'88a.    (See  Article  II.,  '88.) 
'90.    (See  Article  II.,  '90a.) 
'90a.    (See  Article  II.,  '90.) 

'90b.    Notizen   iiber  die  Siisswasser-Calaniden.    Zool.  Anz.,  XIII. 

Jahrg.,  Nos.  349  u.  350,  pp.  629-633,  654-658. 
'91.    tiber  die  pelagische  Fauna  einiger  Seen  des  Schwarzwaldes. 

Zool.  Anz  ,  XIV.  Jahrg.,  No.  355,  pp.  33-38. 
'92.    Zusammenselzung  der  pelagischen  Fauna  der  Siisswasserbecken. 

Biol.  Centralbl.,  XII.  Band.,  Nr.  6,  7  u.  8,  pp.  171-182,  200-205. 
*'93.    Lesorganismes  inferieurs  des  lacs  a  la  region  du  Rhone.  Arch. 

des  Sci.  phys.  et  nat.,  octobre — decembre,  1893. 
'94.    Fauna  hochgelegener  Seen.    Seen  der  Rocky-Mountains,  Nord- 

Amerika.    Von  S.  A.  Forbes.    Biol.  Centralbl.,  XIV.  Bd.,  Nr.  8, 

pp.  287-293. 
'95.    (See  Article  II.) 

'96.  Die  Binnengewiisser-Fauna  der  Azoren  ;  Referat  nach  de  Guerne 
und  Barrois.    Biol.  Centralbl.,  XVI.  Bd.,  Nr.  18,  pp.  683-688. 

Jurine,  L. 
'20.    (See  Article  II.) 

Kafka,  J osef. 
'92.    (See  Article  II.) 

Kerville,  H.    (See  Gadeau  de  Kerville,  H.) 


North  American  Species  of  Diaptomus.  195 


King,  R.  L. 

*'55.    On  Australian  Entomostracans.   Papers  and  Proc.  Roy.  Soc. 
Van  Diemen's  Land,  Vol.  III.,  Pt.  I. 

Koch,  C.  L. 

'35-'41.  Deutschlands  Crustaceen,  Myriapoden,  und  Arachniden, 
Heft.  XXI.,  XXXV.  Regensburg. 

Koelbel,  C. 

'85.    Carcinologisches.    Sitzungsber.  d.  K.  Akad.  d.  Wiss.  Wien, 
Math.-naturw.  Klasse.,  Bd.  XC,  1  Abteil.,  pp.  312-323,  PI.  I.,  Fig. 
-  1-5. 

Kortchaguine,  A.  N. 
*'87.    Fauna  der  Umgebung  Moskaus.    I.  Crustaceen  [German  title 
of  Russian  article].    (Arb.  aus.  d.  Laborat.  d.  Zool.  Mus.  der  Univ. 
Moskau.)  Schriften  der  Gesellsch.  v.  Freunden  d.  Naturwissensch. 
zu  Moskau,  Bd.  LIT. 

Ladenburger,  R. 

'84.  Zur  Fauna  des  Mansfelder  Sees.  Zool.  Anz.,  VII.  Jahrg.,  Nr. 
168,  pp.  299-302. 

Lauterborn,  R. 

'94.    Uber  die  Winterfauna  einiger  Gewasser  der  Oberrheinebene. 

Mit  Beschreibungen  neuer  Protozoen.    Biol.  Centralbl.,  XIV.  Bd., 

Nr.  11,  pp.  391-398. 
'94a.    Beitriige  zur  Siisswasserfauna  der  Insel  Helgoland.  Wissen- 

schaftliche  Meeresuntersuchungen,  "Xeue  Folge,"  Bd.  I.,  Heft  1,  pp. 

216-221. 

Leydig,  Fr. 

'59.  Bemerkungen  iiber  den  Bau  der  Cyclopiden.  Arch.  f.  Naturg. 
X  XV.  Jahrg.,  I.  Bd.,  pp.  194-207,  Taf.  I  V. 

Lilljeborg,  W. 
'53.    (See  Article  II.) 

'63.  Beskrifning  ofver  twa  arter  Crustaceer  af  ordingarne  Ostracoda 
och  Copepoda.  Ofv.  af  K.  Vet.-Akad.  FornandL,  Arg.  XIX.,  p.  391. 

'87.  On  the  Entomostraca  collected  by  Mr.  Leonhard  Stejneger,  on 
Bering  Island,  1882-83.  Contributions  to  the  Natural  History  of 
the  Commander  Islands.    Proc.  U.  S.  Nat'n'I  Mus.,  1887,  pp.  154-156. 

'88.  Descriptions  de  deux  especes  nouvelles  de  Diaptomus  du  nordde 
l'Enrope.    Bull,  de  la  Soc.  zool.  de  France,  T.  XIII.,  pp,  156-158. 

Lubbock,  J. 

*'53.  On  two  New  Species  of  Calanidae,  with  Observations  on  the 
Spermatic  Tubes  of  Pontclla,  Diaptomus,  Ann.  Mag.  Nat.  Hist., 
Vol.  XII.,  pp.  115-124,  159-165,  Pis.  V.,  VI. 


196     Illinois  State  Laboratory  of  Natural  History. 


*'54.  On  the  Fresh-water  Entomostraca  of  South  America.  Trans. 
Entom.  Soc.  N.  S.,  T.  III. 

*'56.  On  some  Entomostraca  collected  by  Dr.  Sutherland  in  the  At- 
lantic Ocean.  Trans.  Entom.  Soc.  London,  Vol.  IV.,  Part  IT.,  pp. 
8-39,  Pis.  II.-XII. 

*'57.  Description  of  eight  New  Species  of  Entomostraca  found  at 
Weymouth.  Ann.  Mag.  Nat.  Hist.,  Vol.  XX.,  pp.  401-410,  Pls.X.,XI. 

*'60.  On  Some  Oceanic  Entomostraca  collected  by  Capt.  Toynbee. 
Trans.  Linn.  Soc.  London,  Vol.  XXIII.,  pp.  295,  296;  Ann.  Mag. 
Nat.  Hist.,  Vol.  XL,  pp.  488,  489. 

'63.    (See  Article  II.) 
Maitland,  R.  T. 

*'74.  Naamlijst  van  Nederlandsche  Schaldieren.  Tijdschr.  Nederl. 
Dierk.  Vereen.,  1  Deel,  pp.  228-269. 

Marenzeller,  E.  v 
'73.    liber  Diaptomus  amblyodon  n.  sp.    Verh.  d.  K.-K.  zool.-bot.  Ge- 
sellsch.  Wien,  Bd.  XXIII.,  p.  593,  Taf.  VI. 

Marsh,  C.  D. 
'91.    (See  Article  II.) 
'92.    (See  Article  II.) 
'93.    (See  Article  II.) 
'93a.    (See  Article  II.) 

'94.    On  two  New  Species  of  Diaptomus.   Trans.  Wis.  Acad.  Sci., 
Arts,  and  Letters,  Vol.  X.,  pp.  15-17,  PI.  I. 
\_D.  mississippiensis  and  D.  birgei,  n.  sp.] 
'95.    (See  Article  II.) 

'97.  On  the  Limnetic  Crustacea  of  Green  Lake.  Trans.  Wis.  Acad. 
Sci.,  Arts,  and  Letters,  A^ol.  XL,  pp.  179-224,  Pis.  V.-X1V. 

Milne-Edwards,  H. 
'34-'40.    (See  Article  II.) 

'38.  Extrait  d'  un  Memoire  sur  la  distribution  geographique  des 
Crustaces.    Compt.  rend,  dee  Seances  de  l'Acad.  des  Sci.    9  pp. 

Moniez,  It. 
'87.    (See  Article  II.) 
'89.    (See  Article  II.,  '89a.) 

Mrazek,  A. 
'91.    (See  Article  II.) 

'93.  Pfi'spevkyk  poznani  sladkovodnich  Copepodu  [Contributions 
to  the  Knowledge  of  Fresh-water  Copepoda].  Vestm'k  Krai.  Ceske 
Spol.  Nauk.  Th'da  math.-ph'r.,  1893.  74  pp.,  8  Pis.;  Abstract,  Zool. 
Centralbl.,  I.  Jahrg.,  pp.  593,  594. 


North  American  Species  of  Diaptomus.  197 


'93.    (See  Article  II.,  '93c.) 
'95.    (See  Article  II.) 

*'96.  Zwr  Entwickelungsgeschichte  einiger  Taenien.f  Sitzungsber. 
d.k.  bohm.  Gesellsch.  Wiss.  Math.-nat.  Classe.  16  pp.,  1  PI. ;  Abstract, 
Zool.  Centralbl.,  IV.  Jahrg.,  No.  15,  pp.  522,  523. 

Muller,  O.  F. 
1792.    (See  Article  II.) 

Nicolet. 

*'48-'49.  Crustaceos.  In  Gay,  C,  Historia  fisica  y  politica  de  Chile 
etc.,  Zoologia,  Vol.  III.,  pp.  288-292. 

Nordqvist,  O. 
'86.    (See  Article  II.) 
'87.    (See  Article  II.) 

'88.  Die  Calaniden  Finlands.  Bidrag  till  Kannedom  af  Finlands 
Natur  och  Folk.  Utgifva  af  Finska  Vetensk.-Soc,  Heft  47,  pp. 
192-275.    10.  Pis. 

'89.  liber  einen  Fall  von  androgyner  Missbildung  bei  Diaptomus 
gracilis  G.  O.  Sars.  Arch.  f.  Naturgesch.  LV.  Jahrg.,  pp.  241-243, 
Taf.  XII. 

'90.    (See  Article  II.) 
Norman,  A.  M. 

'86.  Museum  Normanianum ;  or  a  Catalog  of  the  Invertebrata  of 
Europe  and  the  Arctic  and  North  Atlantic  Oceans,  pp.  22,  23. 

OuchakofF,  N. 

*'55.  Pontie  de  Waearino.  Bull,  de  la  Soc.  imp.  des  natural,  de  Mos- 
cou,  T.  XXVIII. 

Pavesi,  P. 

'79.    (See  Article  II.) 

'79a.    (See  Article  II.) 

'83.    (See  Article  II.) 
Pickering,  C. 

'44.  Generic  Description  of  Scopiphora.  vayans.  Nat.  Hist.  N.  Y., 
Zool.,  Part  VI.,  Crustacea,  p.  (52. 

Pitard,  E. 

*'97.    Sur  le  Plankton  du  lac  de  Joux.    Arch.  Sci.  phys.  et  nat.  I1"1 

per.,  T.  111.  3  pp. 
*'97a.    Sur  le  Plankton  du  lac  Brenet.    Arch.  Sci.  phys.  et  nat.,  4Amo 

prr.,  T.  III.   2  pp. 

Poggenpol,  M.  J. 
'74.    (See  Article  II.)  


tContains  reference  to  Diaptomus- 


198     Illinois  'State  Laboratory  of  Natural  History. 


Poppe,  S.  A. 

'84.    Bemerkungen  zu  K.  Ladenburger's:  Zur  "Fauna  des  Mans- 

felder  Sees"  in  No.  168  des  Zoologischen  Anzeigers.  Zool.  Anz., 

VII.  Jahrg.,  No.  176,  pp.  499,  500. 
'86.    Ein  neuer  Diaptomus  aus  dem  Hirschberger  Thai.   Zeitschr.  f. 

wiss.  Zool.,  Bd.  43,  pp.  285-289,  Taf.  X.,  Fig.  1-12. 
'88.    Diagnoses  de  deux  especes  du  genre  Diaptomus  Westwoocl. 

Bull,  de  la  Soc.  zool.  de  France,  T.  XIII.,  pp.  159,  160. 
'89.    (See  Article  II.) 
'89a.    (See  Article  II.) 

'91.    Ein  neuer  Diaptomus  aus  Brasilien.   Zool.  Anz.,  XIV.  Jahrg., 
No.  368,  pp.  248-250.    3  Fig. 
\_D.  deitersi  n.  sp.] 

Poppe,  S.  A.,  u.  Mrazek,  A. 
'95.    Entomostraken  des  Naturhistorischen  Museums  in  Hamburg. 

1.  Die  von  Herrn  Dr.  F.  Stuhlmann  auf  Zanzibar  und  dem  gegeniiber- 
liegenden  Festlande  gesammelten  Siisswasser-Copepoden.    2.  Taf. 

2.  Entomostraken  von  Siid-Georgien.  1  Taf.  3.  Die  von  Herrn 
Dr.  H.  Driesch  auf  Ceylon  gesammelten  Siisswasser-Entomostra- 
ken.  I  Taf.  Beiheft  zum  Jahrb.  der  Hamburgischen  wissenschaftl. 
Anstalten.  XII.    20  pp. 

Poppe,  S.  A.,  et  Richard,  J. 
'90.    (See  Article  II.) 

'92.  Description  du  Diaptomus  schmackeri  n.  sp.,  recueilli  par  M. 
Schmacker  dans  le  lac  Tahoo  (Chine).  Bull  de  la  Soc.  zool.  de 
France,  T.  XVII.,  pp.  149-151.    6  Fig. 

Rath,  O.  v. 
'91.    (See  Article  II.) 

Rehberg,  H. 
'80.    (See  Article  II.,  '80a.) 
'80a.    (See  Article  II.,  '80b.) 

Richard,  J. 
'87.    (See  Article  II.) 

'87a.  Sur  la  faune  pelagique  de  quelques  lacs  d'Auvergne.  Compt. 
rend.  d'Acad.  des  Sci.,  14  novembre  et  12  decembre,  T.  CV.,  pp. 
951-953. 

'88.    Entomostraces  nouveaux  ou  peu  connus.    Bull,  de  la  Soc.  zool. 

de  France,  T.  XIII.,  p.  156. 
'88a.    (See  Article  II.,  '88.) 

*'89.  Anomalie  de  l'antenne  droite  chez  Diaptomus  coe.rule.us  Fisch., 
male.   Bull,  de  la  Soc.  zool.  de  France,  T.  XIV.,  pp.  38,  39. 


North  American  Species  of  Diaptomus.  199 


'89a.   Note  sur  les  peches  effeetuees  par  M.  Ch.  Rabot  dans  les  lacs 

Enara,Iinanclra,et  clans  leKolozero.  Bull,  de  la  Soc.  zool.de  France, 

T.  XIV.,  pp.  100-109. 
'89b.    Description  du  Mesoclvra  blanchardi,  Copepode  nouveau  des 

Sebkhas  algeriennes.    Bull,  de  la  Soc.  zool.  de  France,  T.  XIV., 

pp.  317-321. 
'90.    (See  Article  II.,  '90c.) 

'90a.  Sur  les  Entomostraces  et  quelques  autres  animaux  inferieurs 
des  lacs  de  l'Auvergne.  Rev.  des  Sci.  Nat.  Appliquees,  37e  Ann., 
lre  Sera.,  No.  10,  pp.  472-481.    10  Fig. 

'90b.    (See  Article  II.,  '90a.) 

'90c.    (See  Article  II.,  '90b.) 

'90d.    Xote  preliminaire  sur  le  systeme  nerveux  de  quelques  especes 
de  Diaptomus.    Bull,  de  la  Soc.  zool.'de  France,  T.  XV.,  pp.  212-219. 
'91.   (See  Article  II.) 
'91a.    (See  Article  II.) 

'91b.  Reeberches  sur  le  systeme  glandulaire  et  sur  le  systeme  ner- 
veux des  Copepodes  libres  d'eau  douce,  suivies  d'une  revision  des 
especes  de  ce  groupe  qui  vivent  en  France.  Ann.  Sci.  nat.  zool.,  T. 
XII.,  pp.  113-270,  PI.  V.-VI1I. 

'92.  Free  Fresh-water  Copepoda.  Ann.  Sci.  Nat.,  Vol.  XII.,  pp.  113- 
270;  Abstract,  Journ.  Roy.  Micr.  Soc,  1892,  p.  478. 

'93.  Copepodes  rccueillis  par  M.  le  Dr.  Tbeod.  Barrois  en  Egypte,  en 
Syrie  et  en  Palestine  (Mars— Juin,  1890).  Rev.  Biol,  du  Xord  de  la 
France,  5e  ann.,  No.  10,  juillet,  1893.    36  pp.,  51  Fig. 

'94.    Entomostraces  recueillis  par  M.  E.  Modigliani  dans  le  Lac  Toba 
(  Sumatra).    Ann.  del  Mus.  Civ.  di  Storia  Nat.  di  Genova,  Ser.  II. »  , 
Vol.  XIV.  (XXXI V.),  Oct.,  1894,  pp.  565-578.  Fig.  9-14. 
I  Diaptomus  doriai  n.  sp.] 

'95.    (See  Article  II., '95a.) 

'95a.    (See  Article  II., '95b.) 

'97.  Sur  quelques  Entomostraces  d'Eau  donee  Mo  environs  de  Buenos 
Aires.  Anales  del  Mus.  Nac.  de  Buenos  Aires,  T.  V.,  pp.  321-332, 
Fig.  1-6. 

[Diaptomus  hergi  n.  sp.] 

'97a.    Entomostraces  recueillis  par  M.  leDireeteur  Steindaclmer  dans 
les  lacs  de  Janina  et  de  Scutari.    Ann.  d.  K.  K.  Naturbist.  llofmus., 
Bd.  XII..  I  left  1,  pp.  63-66,  Fig.  1-4. 
[Diaptomus  steindachneri  n.  sp.] 

'97b.  Entomostraces  de  PAmerique  du  Sud  recueillis  par  MM.  CJ. 
Deiters,  J.  von  Ibering,  G.  W.  Mliller  et  G.  O.  Poppe.  Mem.  de 
la  Soc.  zool.  de  France,  T.  X.,  pp.  263-301,  Fig.  1-45. 


200      Illinois  State  Laboratory  of  Natural  History. 


'97c.  Sur  deux  Entomostraces  d'Eau  donee  reeueillis  par  M.  Chaf- 
fanjon  en  Mongolie.  Bull.  du.  Mus.  d'hist.  nat.,  1897,  No.  4,  pp. 
131-135,  Fig.  1-5. 

[Diaptomus  chaffanjoni  n.  sp.] 

Ruckert,  J. 

*'94.  Zur  Eireifung  bei  Copepoden.  Merkel-Bonnet's  Anat.  Hefte, 
I.  Abt.,  XII.  Heft,  pp.  2G1-351,  Taf.  XX.-XXV.;  Abstract,  Zool. 
CentralbL,  II.  Jahrg.,  No.  10,  pp.  291-295. 

Russki. 

*'89.    Le  faune  pelagique  du  lac  deKabane.   [French  title  of  Russian 
work.]    Trav.  Soc.  imp.  des  nat.  del'Univ.  de  Kasan,  T.  XIX. 
Sars,  G.  O. 
'62.    (See  Article  II.) 
'63.    (See  Article  II.) 
'64.    (See  Article  II.) 

'86.    Crustacea.  II.    Den  norske  Nordhavs-Expedition  1876-78,  pp. 

76-79.  Christiana. 
'89.    On  some  Fresh-water  Ostracoda  and  Copepoda  raised  from  dry 

Australian  mud.    Forh.  i  Vidensk.-Selskab.  i  Christiania,  pp.  1-77, 

PI.  I.-VIII.    (Pis.  I.  and  II.  colored.) 
'95.    On  some  South  African  Entomostraca  raised  from  dried  mud. 

Vidensk.-Selskab.  Skrifter,  I.  Math.-naturw.  Klasse,  1895,  Nr.  8, 

pp.  1-55.    8  Pis. 

[Paracliaptomus  lamellatus,  n.  gen.  and  n.  sp.] 
'96.    On  a  new  Fresh-water  Ostracod,  Stenocypris   chevreuxi,  G.  O. 

Sars,  with  notes  on  some  other  Entomostraca  raised  from  dried 

mud  from  Algeria.  Arch.  f.  Math,  og  Naturvid.  Kristiania.  27  pp., 

3  Pis. 

'97.  Pelagic  Entomostraca  of  the  Caspian  Sea.  Extraitde  1' Annual  re 
du  Musee  Zoologique  de  l'Academie  Imperiales  des  Sci.  de  St.- 
Petersbourg,  1897.    73  pp.,  8  Pis. 

Schmeil,  O. 

'89.    liber  den  Diaptomus  des  salzigen  Sees  (Diaptomus  ?*ichardi  n.  sp.). 

Zool.  Anz.,  XII.  Jahrg.,  No.  323,  pp.  646-64!). 
'91.    (See  Article  II.) 

'92.    Deutschlands  freilebende  Siisswasser-Copepoden.    I.  Teil :  Cy- 

clopidse.    Bibliotheca  Zoologica,  Heft  11.  191  pp.,  8  Pis. 
'94.    (See  Article  II.) 

'94a.    Einige  neue  Harpacticidenformen  des  Siisswassers.  Zeitschr. 

f.  Xaturwissensch.,  Bd.  LXVIL,  pp.  341-350. 
'95.    Neue  Spaltfusskrebse  der  Fauna  der  Provinz  Sachsen.  Zeitschr. 

f.  Naturwissensch.,  Bd.  LX.VIIL,  pp.  126-130. 


North  American  Species  of  Diaptomus.  201 


'96.  Deutschlands  freilebencle  Siisswasser-Copepoden.  III.  Teil: 
Centropagidre.  Abt.  I.  n.  II.  Bibl.  Zoo].  Heft  21,  Lfg.  I.  u.  II., 
Taf.  I.-X1I.,  3  Fig.  in  Text;  Abstract,  Biol.  Centralbl.,  XVI.  Bd., 
Nr.  23,  pp.  845-847. 

'97.  Deutschlands  freilebende  Siisswasser-Copepoden.  Nachtrag. 
Bibl.  Zool.  Heft  21,  Nachtrag,  pp.  145-188,  Taf.  XIII.,  XIV. 

Scott,  T. 

*'94.  Diaptomus  serricornis  Lilljeborg,  in  Lochs  in  Barra  and  North 
Uist.    Ann.  Scot.  Nat.  Hist.,  Oct.,  pp.  258,  259. 

Scourfield,  D.  J. 
'93.    (See  Article  II.) 

'94.    Entomostraca  and  the  Surface-film  of  Water.  Journ.  Linn.  Soc, 

Vol.  XXV.,  Zoology,  No.  158,  pp.  1-19,  Pis.  I.,  II. 
'95.   A  Preliminary  Account  of  the  Entomostraca  of  North  Wales. 

Journ.  Quekett  Micr.  Club,  Vol.  VI.,  Ser.  II.,  No.  37,  pp.  127-143, 

PI.  VIII. 

'97.  Verzeichniss  der  Entomostraken  von  PI  on.  Forschungsber.  a. 
d.  Biol.  Stat,  zu  Plon,  Theil  V.,  pp.  180-183.  Stuttgart. 

Seligo,  A. 
'90.    (See  Article  II.) 

Siebold,  C.  Th. 

*'39.  Beitriige  zur  Naturgeschichte  der  wirbellosen  Thiere.  II.  Uber 
das  Begattungsgeschiift  des  Cyclops  castor.  Neueste  Schrift.  Nat. 
Ges.  Danzig,  Bd.  III.,  Heft  2,  pp.  36-50,  Taf.  2,  Fig.  41-44. 
(Ubersetzt  in:  Ann.  Sci.  Nat.  Paris,  T.  XIV.,  pp.  26-38,  Taf.  V. 
Nach  Giesbrecht.)    [Fide  Schmeil.] 

Sowinsky,  W. 
'91.    (See  Article  II.) 

*'91a.  Sur  la  nouvelle  espece  du  genre  Diaptomus,  trouvee  dans  le 
lac  Ribnoye-Ozero  pros  de  la  ville  Stawropol.  [French  title  of  Rus- 
sian article.]  Mem.  de  la  Soc.  des  natural,  de  Kiew,  T.  XI.,  Part  I. 
4  pp.,  1  Fig.  in  text. 

Steck.  Th. 

'93.  Beitriige  zur  Biologie  des  grossen  Moosseedorfsees.  Mitt.  d. 
naturf.  Gesellsch.  in  Bern,  Jahrg.  1893,  pp.  20-73. 

Stuhlmann,  F. 

'91.  Beitrage  zur  Fauna  cent ral-af rikanischer  Seen.  Zool.  Jahrb., 
Abteil.  f.  System.,  Bd.  V.,  pp.  924-92(5. 

Szekely,  B. 

*'82.  Tanulmanyok  a  Diaptomus  petefejlodesenek  elso  phasisairol  a 
blastoderma  fellepesi'ig.    KolozsvAi  t. 


202     Illinois  State  Laboratory  of  Natural  History. 


Thallwitz,  J. 

*'91.  Die  Siisswasser-Calaniden  Deutschlands.  Nat.  Rundschau.  Bd. 
VI.,  pp.  131, 132.  Berlin. 

Turner,  C.  H. 
'92.    (See  Article  II.) 

Ulianin,  W.  N. 

*'74.  Cladoceren  und  Oopepoden  einiger  Seen  des  centralen  Russ- 
lands.  Schriften  d.  Gesellsch.  v.  Freunden  der  Naturwissensch., 
etc.,  zu  Moskau,  Bd.  X.,  Abt.  II.,  pp.  78-81. 

'75.  Crustaceen  von  Turkestan.  Reise  A.  P.  Fedtschenko's  in  Turk- 
estan. [German  title  of  Russian  article.]  Schrift.  de  Gesellsch.  v. 
Freunden  der  Naturwissensch.,  etc.,  zu  Moskau,  Bd.  XL,  Abt.  VI., 
Copepoden,  pp.  22-41,  Taf.  VI.-XII. 

Underwood,  L.  M. 
'86.    (See  Article  II.) 

Vejdovsky,  F. 

'82.  Thierische  Organismen  der  Brunnengewasser  von  Prag.  66 
pp.,  8  Pis.  Prag. 

Villepoix,  R.  M.  de 
'88.    (See  Article  II.) 

Vosseler,  J. 
'86.    (See  Article  II.) 
'89.    (See  Article  II.) 

'91.  Die  Krebsfauna  unserer  Gewasser.  In  Zacharias's  "Die  Thier- 
und  Pflanzen welt  des  Siisswassers,,,  Bd.  L,  pp.  323-380.  6  Fig.  Leip- 
zig. 

Weber,  Max. 

'92.  On  the  Fresh-water  Crustacea  of  the  Indian  Archipelago  with 
Observations  on  the  Fauna  of  Fresh-water  in  General.  Ann.  Nat. 
Hist.,  Ser.  6,  Vol.  XIV.,  pp.  237-253. 

'92a.  Die  Susswasser-Crustaceen  des  Indischen  Archipels,  nebst  Be- 
merkungen  iiber  die  Siisswasser-Fauna  im  AUgemeinen.  Zool.  Er- 
geb.  einer  Reise  in  Niederland.  Ost-Ind.,  pp.,  528-571,  Taf.  XXX. 
Leiden. 

Westwood,  J.  O. 
*'36.   Cyclops.   Partington's  Cyclopedia.  Xat.  Hist. 

Wierzejski,  A. 

'82.  Materyjaly  do  fauny  jezior  tatrzanskich.  [Materials  for  the 
Fauna  of  the  Karpathian  Lakes.]  Copepoden.  Sprawozd.  Kom. 
fiz.  Akad.  Umiej.,  T.  XVL,  pp.  233,  234,  Taf.  III. 


North  American  Species  of  Diaptomus.  203 


*'83.  Zarys  fauny  stawow  tatrzailskich.  Pamietn.  Tow.  tatrz.,  T. 
VIII.  Krakau. 

'87.  O  Krajowych  skorupiakach  z  rodziny  Calanidae.  [On  the  na- 
tive Copepoda  of  the  Family  Calanidas.]  Rozpr.  i  Sprawozd. 
Wydz.  mat.-przyr.  Akad.  Umiej.  Krakow,  T.  XVI.    13  pp.,  1  PI. 

'95.  Przeglad  fauny  skorupiakow  galieyjskich.  [Review  of  the 
Crustacean  Fauna  of  Galieia.]    (See  Article  II.  for  citation.) 

Wille,  N. 

'96.  Mitteilungen  aus  der  biologischen  Gesellschaft  in  Christiania. 
Biol.  Centralbl.,  XVI.  Bd.,  Mr.  3,  p.p.  124-126. 

Zacharias,  O. 

*'85.    Studien  iiber  die  Fauna  des  Grossen  und  Kleinen  Teichs  im 
m  Riesengebirge.    Zeitschr.  f.  wiss.  Zool.,  Bd.  XLI.,  pp.  483-516,  Taf. 

XXVI. 
'87.    (See  Article  II.) 

'87a.    Zur  Entomostrakenfauna  der  Umgebung  von  Berlin.  Biok 

Centralbl.,  Bd.  VII.,  Nr.  5,  pp.  137-139. 
'87b.    (See  Article  II.) 
'88.    (See  Article  II.,  '88a.) 

'88a.  Die  Tierwelt  der  Eifelmaare.  Biol.  Centralbl.,  VIII.  Bd.,  Nr.  18, 
p.  574. 

'88b.  tiber  die  geographische  Verbreitung  des  Genus  Diaptomus. 
Biol.  Centralbl.,  VIII.  Bd.,  Nr.  18,  p.  575. 

'89.  Bericht  iiber  eine  Zoologische  Exkursion  an  die  Kraterseen  der 
Eifel.   Biol.  Centralbl.,  IX.  Bd.,  Nos.  2,  3,  pp.  56-G4,  76-80. 

'90-'91.  tiber  ein  interessantes  Kapitel  der  Seenkunde.  Biol.  Cen- 
tralbl., X.  Bd.,  Nr.  18,  pp.  123-128. 

'93.  Fauna  des  grossen  Pinner  Sees.  Forschungsber.  aus  der  Biol. 
Station  zu  Plon,  Theil  I.,  pp.  3-13;  Extract,  Biol.  Centralbl.,  XI II. 
Bd.,  Nr.  11  u.  12,  pp.  377-382. 

'94.  Faunistische  jNIitteilungen.  Fauna  des  grossen  Ploner  Sees. 
Forschungsber.  aus  der  Biol.  Stat,  zu  Plon,  Teil.  II.,  pp.  57-66. 

'95.  iiber  die  horizontale  und  vertikale  Verbreitung  limnetischer 
Organismen.  Forschungsber.  aus  der  Biol.  Stat,  zu  Plon.  Theil  III., 
pp.  118-128.  Extract,  Biol.  Centralbl.,  XIII.  Bd.,  Nr.  11  u.  12,  pp. 
377-382. 

'95a.  Statistische  Mitteilungen  aus  der  Biologischen  Station  am 
grossen  Ploner  See.  Zool.  Anz.,  XVIII.  Jahrg.,  pp.  28,70,  87,  125, 
140, 190,  256,  305,  367,  414,  448. 

'96.  Quantitative  Untersuchungen  iiber  das  Limnoplankton.  64  pp. 
Berlin. 


204      Illinois  State  Laboratory  of  Natural  History. 


'97.  Biologische  Beobachtungen  an  den  Versuehsteichen  cles  Schles. 
Fischerei-vereins  zu  Trachenberg.  Forschungsber.  a.  d.  Biol.  Stat, 
zu  Plon,  Theil  V.,  pp.  10-28.  Stuttgart. 

Zaddach,  E.  G. 

'44.  Synopseos  Crustaceorum  Prussicorum  Proclromus.  Dissertatio 
Zoologica.   47  pp.   Regiomonti  (Konigsberg).. 

Zenker,  W. 
'54.    (See  Article  II.) 

'54a.    System  der  Crustaceen.    Arch.  f.  Naturgesch.,  XX.  Jahrg., 

Bd.  I.,  pp.  108-118. 
'54b.    Critik  der  Erichson'schen  Glieclmassentheorie.    Arch.  f.  Na- 

turgesch.,  XX.  Jahrg.,  Bd.  I.,  pp.  118-138. 

Zograf,  N.  ♦ 
*'96.    Essai  d'explication  de  l'origine  de  la  faune  des  lacs  de  la  Rus- 
sie  d'Europe.  Compt.  rend,  des  seance  du  troisieme  congres  internat. 
de  Zool.,  Leyde,  16-21  sept.,  1895,  pp.  183-195.   Leyde.  Abstract, 
Zool.  Centralbl.,  III.  Jahrg.,  No.  14,  pp.  481-483. 

Zopf,  W. 

'95.  Conn's  Hiimatoehrom  ein  Sammelbegriff.  Biol.  Centralbl.,  XV. 
Bd.,  Nr.  11,  pp.  417-427. 

Zschokke,  P. 
'90.    (See  Article  II.) 
'90a.    (See  Article  II.) 
'91.    (See  Article  II.) 

*'91a.    Die  zweite  zoologische  Excursion  an  die  Seen  des  Rhatikon. 

Verhandl.  Naturf.  Gesellsch.  Basel,  Bd.  IX.,  2  Teil,  pp.  425-508; 

Abstract,  Journ.  Roy.  Micr.  Soc,  1892,  p.  194. 
'94.    Die  Tierwelt  der  Juraseen.    Rev.  Suisse  cle  Zool.  et  Ann.  du 

Mus.  d'hist.  nat.  de  Geneve,  T.  II.,  Liv.  II.,  pp.  349-376,  PI.  XIV. 
'94a.    Die  Fauna  hoch  gelegener  Gebirgsseen.    Ein  Beitrag  zur 

Kenntniss  der  Vertikalen  Verbreitung  niederer  Tiere.   Verh.  d. 

Naturf.  Gesellsch.  in  Basel,  Bd.  XI.,  Heft  1,  pp.  36-133,  Taf.  I. 
'95.    Die  biologische  Station  zu  Plon  nach  den  Forschungsberichten. 

Teil  II.  u.  III.    Biol.  Centralbl.,  XV.  Bd.,  Nr.  10,  pp.  408-415. 


North  American  Species  of  Diaptomus. 


205 


EXPLANATION  OF  PLATES. 

Plate  XXI. 

Fig.  1.    Diaptomus  sicilis,  fifth  feet  of  male.    X  280. 

Fig.  2.    Fifth  feet  of  female  of  same  (minus  one  outer  ramus).    X  280. 

Fig.  3.    Last  thoracic  segment  and  abdomen  of  female  of  same.    X  140. 

Plate  XXII. 

Diaptomus  piscina,  fifth  feet  of  male. 

Fifth  foot  of  female  of  same  (Portage  Slough  specimen).  X  280. 
Last  thoracic  segment  and  abdomen  of  female  of  same.  X  140. 
Fifth  foot  of  female  (Yellowstone  Park  specimen).    X  280. 

Plate  XXIII. 

Diaptomus  sanguineus,  second  basal  segment  of  right  fifth  foot 

of  male.    X  210. 
Terminal  segments  of  right  male  antenna  of  same.    X  210. 

Plate  XXIV. 

Diaptomus  sanguineus,  first  abdominal  segment  of  female,  seen 

from  the  side.    X  110. 
Last  thoracic  and  first  abdominal  segments  of  female  of 

same.    X  110. 
Fifth  feet  of  male  of  same.    X  210. 

Dorsal  outline  of  female  of  same,  showing  hump.    X  110. 
Plate  XXV. 

Fig.  1,2.    Diaptomus  sanguim  us,  fifth  foot  of  female.    X  240. 
Fig.  3,  4.    Rigbt  fifth  foot  of  male  of  same.    X  210. 
Fig.  5.      Fifth  feet  of  male  of  same  (variant).   X  210. 

Plate  XXVI. 

Fig.  1.    Diaptomus  slwshonr,  last  thoracic  segment  and  abdomen  of 

female.    X  80. 
PIG.  2.    Fifth  foot  of  female  of  same.    X  280. 
Fi<;.  3.    Abdomen  of  male  of  same.    X  128. 

Plate  XXVII. 

FlG.  1.  Diaptomus  Union! ,  fifth  feet  of  male.    X  280. 

FlG.  2.  Diaptomus  pallidas,  fifth  foot  of  female.    X  280. 

Fig.  3.  Fifth  feet  of  male  of  same.    X  280. 

Fig.  4.  Diaptomus  albuquerquensis,  fifth  feet  of  male.    X  100. 


Fig.  1-5. 
Fig.  6-8. 


Fig.  1, 2. 

Fig.  3. 

Fig.  4. 
Fig.  5,6. 


206      Illinois  State  Laboratory  of  Natural  History 


Plate  XXVIII. 

Fig.  1.    Diaptomus  reighardi,  fifth  feet  of  male.    X  400. 
Fig.  2.    Diaptomus  stagnalis,  right  antenna  of  male.    X  80. 

Plate  XXIX.* 

Fig.  1.  Diaptomus  oregonensis,  fifth  feet  of  male.    X  240. 

Fig.  2.  Fifth  foot  of  female  of  same.    X  300. 

Fig.  3.  Diaptomus  signicauda,  fifth  feet  of  male.    X  200. 

Fig.  4.  Terminal  segments  of  right  antenna  of  male  of  same.    X  200. 

Fig.  5.  Fifth  foot  of  female  of  same.    X  200. 

Fig.  6.  Last  thoracic  segment  and  abdomen  of  female  of  same.    X  100. 
Plate  XXX.* 

Fig.  1.  Diaptomus  franciscanus,  last  thoracic  segment  and  abdomen 
of  female.  X  40. 

Fig.  2.  Terminal  segments  of  right  antenna  of  male  of  same.  X  200. 

Fig.  3.  Fifth  pair  of  feet  of  male  of  same.  X  200. 

Fig.  4.  Fifth  foot  of  female  of  same.  X  200. 

Fig.  5.  Diaptomus  minutus,  fifth  foot  of  female.  X  300. 

Fig.  6.  Fifth  foot  of  male  of  same.  X  300. 

Fig.  7.  Terminal  segments  of  right  antenna  of  male  of  same.  X  300. 

Fig.  8.  Last  thoracic  segment  and  abdomen  of  female  of  same.  X  250. 

Plate  XXXI. 

Fig.  1.*    Diaptomus  trybomi,  terminal  segments  of  right  male  antenna. 
X  160. 

Fig.  2.*    Last  thoracic  segment  and  abdomen  of  female  of  same,  seen 

from  right  side.    X  96. 
Fig.  3.     The  same,  seen  from  above.    X  140. 
Fig.  4.*    Fifth  pair  of  feet  of  male  of  same.    X  210. 
Fig.  5.*    Fifth  foot  of  female  of  same.    X  240. 

Plate  XXXII. 

Fig.  1.    Diaptomus  ashlandi,  fifth  pair  of  feet  of  female  (a  variant). 
X  240. 

Fig.  2.   Fifth  foot  of  female  of  same.    X  240. 
Fig.  3.   Fifth  pair  of  feet  of  male  of  same.    X  240. 
Fig.  4.    Anterior  fifteen  segments  of  right  antenna  of  male  of  same. 
X  240. 

*Afterde  Guerne  and  Richard,  '89b. 


North  American  Species  of  Diaptomus.  207 

Plate  XXXIII. 

Fig.  1.    Diaptomus  missis sippiensis,  last  thoracic  segment  and  abdomen 

of  male.    X  256. 
Fig.  2.   Fifth  foot  of  female  of  same.    X  256. 
Fig.  3.   Fifth  pair  of  feet  of  male  of  same.    X  256. 
Fig.  4.    Abdomen  of  female  of  same  seen  from  below  (Prof.  Marsh's 

specimen).    X  256. 

Plate  XXXIV. 

Fig.  1.    Diaptomus  clavipes,  right  fifth  foot  of  male  (inner  ramus  want- 
ing).   X  280. 
Fig.  2.   Eight  antenna  of  male  of  same.    X  140. 
Fig.  3.   Fifth  foot  of  female  of  same.    X  400. 

Plate  XXXV. 


Fig.  1. 
Fig.  2. 


Diaptomus  clavipes,  fifth  feet  of  male.    X  280. 

Last  thoracic  segment  and  abdomen  of  female  of  same.   X  140. 


INDEX. 


(Synonyms  i 

Amphaskandria,  102. 
Candacidae,  104. 

Centropagida?,  97,  101, 102, 103. 
Centropagina,  103. 
Cyclops,  100,  106,  141. 
Cyclops,  97, 106, 132. 

longicor?iis,  130. 
Cyclopsina,  97,105. 
Diaptomus,  102, 103,  105. 

albuquerquensis,  98,  113,  115, 
146,  176,  183. 

ambiguus,  177. 

armatus,  133, 135, 136. 

ashlaudi,  98,100,  111,  120, 124, 
158,  167,  183. 

bacillifer,107. 

birgei,  99. 108, 117,  172. 

caroli,  181. 

castor,  98, 106. 

castor,  130. 

cJavipes,98,108,119,127,178,184 
cceruleus,  107. 
deitersi,  99. 
drieschi,  99. 

eiseni,  98,110,115, 162,166,183. 
franciseanus,  98,  110, 118, 132, 

160,166,  182, 183. 
fresnanus,  176,  178. 
gibber,  99. 
giganteus,  138. 
gracilis,  98, 173, 182. 
graciloides,  98. 
incongruens.  99. 
kentuckyensis,  97, 130,  132. 
leptopus,  97,  112, 117, 125, 127, 

130, 135, 181, 182. 
111110111,113,118,127,134,160,182 
longicornis,  132. 

var.  leptopus,  130,  132. 
var.  sirailis,  132, 162,  182. 
minnetonka.  133,  135,  136,  138. 
minutus,  98, 106,  111,  116,  129, 

134,  156,  183. 
mississippiensis,  98,  109,  122, 

149,  173, 184. 
novamexicanus,  99,  111,  116, 

149,  183. 
oregonensis,  109,  119, 124,151, 

169,  171,  183. 


n  Italics.) 

Diaptomus — continued. 

pallidus,  100,  108, 121, 124, 137, 
144, 156, 183. 
var.  sicilis,  122. 
piscinae,  98,  109.116,118,  125, 

127, 181, 182. 
reighardi,  98, 109, 121, 169,184. 
roubaui,  166. 
salinus.  99. 

sanguineus,  97,  112,  117,  12&, 
133, 160, 166, 183. 

serricornis,  162. 

shoshone,110,116, 141,164,183. 

sicilis,  97,  100,  111,  121,  122, 
145, 155,  169, 182, 
var.  imperfectus,  124, 158,167, 
169. 

siciloides,  98, 1 00, 114, 121, 124, 

137,  146,  154,  157,  165, 
166, 181,182. 183. 

signicauda,  98,  114,  120,  157, 

159,  160,  164, 183. 
signicaudatus ,  164. 
similis,  132, 182. 
stagnalis,  97, 113, 115, 129,  136, 

138,  141,142,164, 183. 
trybomi,98,112,120,158,166,183 
tyrrelli,  99,- 108, 119, 160,  176, 

184. 

wierzejskii,  107. 

zachariasi,  99. 
Epischura,  97, 102, 103, 166. 

nevadensis.  98, 168. 

nordenskioldi,  98. 
Glaucea,  97, 105. 
Gymnoplea,  102. 
Heterarthrandria,  102. 
Heterochaetina,  104. 
Heterocope,  99. 
Leuckartiina,  104. 
Limnocalanus,  102,  104. 

sinensis,  99. 
Monoculus,  97,  105. 
Osphranticum,  97, 102, 104. 
Podoplea,  105. 
Pontellidae,  102. 
Temorella,  99. 
Temorina,  103. 
Volvox,  141. 


Plate  XXI. 


Plate  XXII. 


4 


Plate  XXIII. 


Plate  XXV. 


Plate  XXVI. 


Plate  XXVII. 


Plate  XXVIII. 


Plate  XXIX. 


Plate  XXX. 


Plate  XXXI. 


Plate  XXXIII. 


'L. 


